I have the same exact problem.. cept mines idles around 1100 1200 and if i press the brakes... turn the headlights on it drops down to 700 800 rpm the shifter shakes side to side.. like an engine mount is terribly bad!!... when i turn on the a/c it drops down to 700 800.. and the shifter shakes side to side as well... i dont know.. i hate idle problems... i can also hear little backfires coming out the exhaust.. when the car idles at 1100-1200 but when i have the a/c on or when the rpm drops to 800 rpm.. theyre not there..

 

igot screwy idle probs too, only mine dies when iput ti in drive (auto) and surges 200-800-rpm in park and neutral.

 

sounds like a timing issue 13B2quickny

 

i hear little backfires too at idle until at about 2000rpm-3000rpm can that be a timing problem

 

i think i found what it might be it is the tb mod