new o2 sensor still throws code
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To OP: Nonfoulers will not help. They do exactly what they're called. They don't let the plug foul. Now if you can get some Code Nonthrowers, A.K.A. O2 simulators, you'll be good to go.
If I recall correctly, I got that code from a dirty MAF. A dirty MAF can cause the air reading to be artificially low, triggering the computer to make you lean. Which, in turn, can cause the O2 voltage to go out of bounds.
If this is your case, you'll probably also notice some hesitation in the engine under heavy accelearation.
If you can get a hold of a scan tool/software that maps out the O2 sensor waveforms, you should be able to see very easily if the two are off from each other or if one is flat-lining on you.
The only way to tell for sure if a sensor is on the fritz is to get a tool that can show you the waveforms being put out by the sensors. (Which is a bit of an investment.) It could be a wiring problem and GM has a special procedure in the factory manual for confirming a wiring issue - but you need a scan tool that can read the sensors.
I would suggest that you first see how your clean filters and MAF do for you. From my experience, it seems that the MAF readings are dominant over all the O2 sensor readings, which is why I suggest trying them first. (Its also a cheap and easy thing to do.)
Do you know someone who can tune the car? 





