I have a MT Scion TC.
Key detail on the heavy acceleration out of sharp turn is this usually only happens when I've been engine braking into the turn, and not every time. I'm not certain on the rougher/throatier idle (might just be that I have windows down now), but I do think it's there.
AFR is fine and so far I'm not throwing any codes.
I have not yet done any engine valve clearance. There is no actual shimming on this engine, just swapping out lifters.
What else could this be? Timing chain? I do drive this car very hard. 130k miles. What kind of shop should I consider taking it to?
I can inspect muffler, but don't think I'm going to find any holes. On second though, perhaps one of the connections is a bit loose? Eh, the growl goes away soon as I let off on the throttle, and doesn't return, even if I step on it again immediately.
Edit: on second thought, I think I have only heard it while accelerating after turning sharply to the right.