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EDIT: Additional information provided by LovelyWife(TM) - listening outside the car, she has proclaimed that the rattle / buzz / drone / resonance is coming from the front of the car and sounds like it's coming from below the engine between the wheels.

I was overly optimistic in my assessment of the previous question: How should I diagnose an exhaust "howl" when descending through 3200 rpms?

Here is the current situation on my currently all-stock (intake and exhaust tracts) 2004 Subaru Impreza WRX: when revving carefully around 3250 rpms (+/- 100 rpms), there is a distinct jump in the overall noise level on a totally different peak frequency (higher by about an octave on my uncalibrated ears) from the standard exhaust note. This is a super-annoying drone that is easily sustained and right at a convenient cruising speed.

This isn't present (or is greatly reduced) under acceleration but is very obvious at a steady speed or when descending through that rev band. This induces me to think that the problem is downstream of the turbo as it's most obvious in an off-boost situation.

Here's what I know so far:

1. It's not the stock muffler - the problem was much more obvious but still present in the aftermarket muffler.
2. It's not the aftermarket muffler - see 1.
3. It's not the gasket on the muffler - replaced.
4. It's not the nearby heat shielding - same problem with and without the shielding.
5. It's very hard to tell if the problem exists with the muffler removed entirely as it's swamped but all the other noise (or song, depending on your preference).
6. It doesn't appear to be the donut ring on the intermediate pipe after visual inspection.
7. There don't appear to be any obvious holes or leaks in the exhaust tract downstream of the turbo after crawling around under the car all morning.

So, questions:

1. Am I hearing the resonator on the intermediate pipe fail?
2. Am I hearing the pre-cat on the uppipe fail? This is a fabled bogeyman since the WRX was first introduced to the US.
3. If there really is a hidden exhaust leak, why would it be so tightly bound to a single rev range?

EDIT: Additional information provided by LovelyWife(TM) - listening outside the car, she has proclaimed that the rattle / buzz / drone / resonance is coming from the front of the car and sounds like it's coming from below the engine between the wheels.

I was overly optimistic in my assessment of the previous question: How should I diagnose an exhaust "howl" when descending through 3200 rpms?

Here is the current situation on my currently all-stock (intake and exhaust tracts) 2004 Subaru Impreza WRX: when revving carefully around 3250 rpms (+/- 100 rpms), there is a distinct jump in the overall noise level on a totally different peak frequency (higher by about an octave on my uncalibrated ears) from the standard exhaust note. This is a super-annoying drone that is easily sustained and right at a convenient cruising speed.

This isn't present (or is greatly reduced) under acceleration but is very obvious at a steady speed or when descending through that rev band. This induces me to think that the problem is downstream of the turbo as it's most obvious in an off-boost situation.

Here's what I know so far:

1. It's not the stock muffler - the problem was much more obvious but still present in the aftermarket muffler.
2. It's not the aftermarket muffler - see 1.
3. It's not the gasket on the muffler - replaced.
4. It's not the nearby heat shielding - same problem with and without the shielding.
5. It's challenging to tell if the problem exists with the muffler removed entirely as it's swamped but all the other noise (or song, depending on your preference).
6. It doesn't appear to be the donut ring on the intermediate pipe after visual inspection.
7. There don't appear to be any obvious holes or leaks in the exhaust tract downstream of the turbo after crawling around under the car all morning.

So, questions:

1. Am I hearing the resonator on the intermediate pipe fail?
2. Am I hearing the pre-cat on the uppipe fail? This is a fabled bogeyman since the WRX was first introduced to the US.
3. If there really is a hidden exhaust leak, why would it be so tightly bound to a single rev range?

EDIT: Additional information provided by LovelyWife(TM) - listening outside the car, she has proclaimed that the rattle / buzz / drone / resonance is coming from the front of the car and sounds like it's coming from below the engine between the wheels.

I was overly optimistic in my assessment of the previous question: How should I diagnose an exhaust "howl" when descending through 3200 rpms?

Here is the current situation on my currently all-stock (intake and exhaust tracts) 2004 Subaru Impreza WRX: when revving carefully around 3250 rpms (+/- 100 rpms), there is a distinct jump in the overall noise level on a totally different peak frequency (higher by about an octave on my uncalibrated ears) from the standard exhaust note. This is a super-annoying drone that is easily sustained and right at a convenient cruising speed.

This isn't present (or is greatly reduced) under acceleration but is very obvious at a steady speed or when descending through that rev band. This induces me to think that the problem is downstream of the turbo as it's most obvious in an off-boost situation.

Here's what I know so far:

1. It's not the stock muffler - the problem was much more obvious but still present in the aftermarket muffler.
2. It's not the aftermarket muffler - see 1.
3. It's not the gasket on the muffler - replaced.
4. It's not the nearby heat shielding - same problem with and without the shielding.
5. It's very hard to tell if the problem exists with the muffler removed entirely as it's swamped but all the other noise (or song, depending on your preference).
6. It doesn't appear to be the donut ring on the intermediate pipe after visual inspection.
7. There don't appear to be any obvious holes or leaks in the exhaust tract downstream of the turbo after crawling around under the car all morning.

So, questions:

1. Am I hearing the resonator on the intermediate pipe fail?
2. Am I hearing the pre-cat on the uppipe fail? This is a fabled bogeyman since the WRX was first introduced to the US.
3. If there really is a hidden exhaust leak, why would it be so tightly bound to a single rev range?

EDIT: Additional information provided by LovelyWife(TM) - listening outside the car, she has proclaimed that the rattle / buzz / drone / resonance is coming from the front of the car and sounds like it's coming from below the engine between the wheels.

I was overly optimistic in my assessment of the previous question: How should I diagnose an exhaust "howl" when descending through 3200 rpms?

Here is the current situation on my currently all-stock (intake and exhaust tracts) 2004 Subaru Impreza WRX: when revving carefully around 3250 rpms (+/- 100 rpms), there is a distinct jump in the overall noise level on a totally different peak frequency (higher by about an octave on my uncalibrated ears) from the standard exhaust note. This is a super-annoying drone that is easily sustained and right at a convenient cruising speed.

This isn't present (or is greatly reduced) under acceleration but is very obvious at a steady speed or when descending through that rev band. This induces me to think that the problem is downstream of the turbo as it's most obvious in an off-boost situation.

Here's what I know so far:

1. It's not the stock muffler - the problem was much more obvious but still present in the aftermarket muffler.
2. It's not the aftermarket muffler - see 1.
3. It's not the gasket on the muffler - replaced.
4. It's not the nearby heat shielding - same problem with and without the shielding.
5. It's very hard to tell if the problem exists with the muffler removed entirely as it's swamped but all the other noise (or song, depending on your preference).
6. It doesn't appear to be the donut ring on the intermediate pipe after visual inspection.
7. There don't appear to be any obvious holes or leaks in the exhaust tract downstream of the turbo after crawling around under the car all morning.

So, questions:

1. Am I hearing the resonator on the intermediate pipe fail?
2. Am I hearing the pre-cat on the uppipe fail? This is a fabled bogeyman since the WRX was first introduced to the US.
3. If there really is a hidden exhaust leak, why would it be so tightly bound to a single rev range?

I was overly optimistic in my assessment of the previous question: How should I diagnose an exhaust "howl" when descending through 3200 rpms?

Here is the current situation on my currently all-stock (intake and exhaust tracts) 2004 Subaru Impreza WRX: when revving carefully around 3250 rpms (+/- 100 rpms), there is a distinct jump in the overall noise level on a totally different peak frequency (higher by about an octave on my uncalibrated ears) from the standard exhaust note. This is a super-annoying drone that is easily sustained and right at a convenient cruising speed.

This isn't present (or is greatly reduced) under acceleration but is very obvious at a steady speed or when descending through that rev band. This induces me to think that the problem is downstream of the turbo as it's most obvious in an off-boost situation.

Here's what I know so far:

1. It's not the stock muffler - the problem was much more obvious but still present in the aftermarket muffler.
2. It's not the aftermarket muffler - see 1.
3. It's not the gasket on the muffler - replaced.
4. It's not the nearby heat shielding - same problem with and without the shielding.
5. It's very hard to tell if the problem exists with the muffler removed entirely as it's swamped but all the other noise (or song, depending on your preference).
6. It doesn't appear to be the donut ring on the intermediate pipe after visual inspection.
7. There don't appear to be any obvious holes or leaks in the exhaust tract downstream of the turbo after crawling around under the car all morning.

So, questions:

1. Am I hearing the resonator on the intermediate pipe fail?
2. Am I hearing the pre-cat on the uppipe fail? This is a fabled bogeyman since the WRX was first introduced to the US.
3. If there really is a hidden exhaust leak, why would it be so tightly bound to a single rev range?

EDIT: Additional information provided by LovelyWife(TM) - listening outside the car, she has proclaimed that the rattle / buzz / drone / resonance is coming from the front of the car and sounds like it's coming from below the engine between the wheels.

I was overly optimistic in my assessment of the previous question: How should I diagnose an exhaust "howl" when descending through 3200 rpms?

Here is the current situation on my currently all-stock (intake and exhaust tracts) 2004 Subaru Impreza WRX: when revving carefully around 3250 rpms (+/- 100 rpms), there is a distinct jump in the overall noise level on a totally different peak frequency (higher by about an octave on my uncalibrated ears) from the standard exhaust note. This is a super-annoying drone that is easily sustained and right at a convenient cruising speed.

This isn't present (or is greatly reduced) under acceleration but is very obvious at a steady speed or when descending through that rev band. This induces me to think that the problem is downstream of the turbo as it's most obvious in an off-boost situation.

Here's what I know so far:

1. It's not the stock muffler - the problem was much more obvious but still present in the aftermarket muffler.
2. It's not the aftermarket muffler - see 1.
3. It's not the gasket on the muffler - replaced.
4. It's not the nearby heat shielding - same problem with and without the shielding.
5. It's very hard to tell if the problem exists with the muffler removed entirely as it's swamped but all the other noise (or song, depending on your preference).
6. It doesn't appear to be the donut ring on the intermediate pipe after visual inspection.
7. There don't appear to be any obvious holes or leaks in the exhaust tract downstream of the turbo after crawling around under the car all morning.

So, questions:

1. Am I hearing the resonator on the intermediate pipe fail?
2. Am I hearing the pre-cat on the uppipe fail? This is a fabled bogeyman since the WRX was first introduced to the US.
3. If there really is a hidden exhaust leak, why would it be so tightly bound to a single rev range?