[blue00gt]

I don't believe that the Prochamber could change the air/fuel ratio apppreciably. The freed up exhaust just allows the motor to pump air and fuel through at a higher rate - this extra air coming in is measured by the mass air meter, so there should be no problem there. Even without cats the mil eliminators should be feeding the right voltage to the sensors, and the O2 sensors are only responsible for fine-tuning the mixture and indicating problems and should not be able to have that drastic of an effect on idle speed even with no cats and no mil eliminators. Also, if the computer were hunting and causing the problem, the cycle time of the problem he describes would be alot faster.
If the problem coincides with the A/C compressor coming on with the defroster you should be able to hear a loud click when it turns on and the idle speed drops. Getting the refrigerant refilled on my GT fixed the problem without doing anything else. I'm just saying to look into it because I had the exact same problem and that's what it turned out to be with my car, silly as it sounds. I don't know why having low refrigerant would make the idle change when it kicks in any more noticeable that when the system is filled - maybe it was just that it kept coming on and off alot more often.