I can not point out any one specific item that will help your car pass.
But for your greater Phoenix area location I would start, after you run through your tank of fresh gas, by parting with the $17 dollars for the first test.
This will provide a reference of where your at on emissions, you might even pass.
It will also show if your more then twice the allowed emissions which presents it own set of issues for passing and for waivers.
The reason for this is that for the Phoenix area after two fails you are allowed a request for waiver. The waiver is allowed if total repairs will exceed $450.
All cost related to repairs for 60 days prior to making the attempt to pass count toward this $450. So document the automotive parts you have spent so far (plugs, additives, parts changed).
Check myAZcar.com for details.

I can not point out any one specific item that will help your car pass.
But for your greater Phoenix area location I would start, after you run through your tank of fresh gas, by parting with the $17 dollars for the first test.
This will provide a reference of where your at on emissions, you might even pass.
Testing will provide areas that are off and can help focus repairs.

It will also show if your more then twice the allowed emissions which presents it own set of issues for passing and for waivers.

Another reason getting through the first test is that for the Phoenix area after two fails you are allowed a request for waiver. If the car can not be repair at a reasonable cost and everything reasonable has been done to lower emissions then the waiver is allowed if total repairs will exceed $450.
All cost related to repairs for 60 days prior to making the attempt to pass count toward this $450. So document the automotive parts you have spent so far (plugs, additives, parts changed).
Check myAZcar.com for details.