ok, the idle air control valve(IAC) it a controlled vac. leak that the pcm uses to control the idle speed. the pcm tires to keep the idle at a certain rpm , no matter whatt is causing it to come down. if you put it in gear, it will drop for a sec then come back up. turn the air on and it does the same, as well as turning the steering wheel. the IAC is on the side of the TB. take it off and use cleanner to get the carbon off of it. then use a senor safe cleanner to clean the seat in the TB where it sits. when you put it back together, it may take a little to get started because of the cleanner that you sprayed in the TB. once it idles, let it learn the idle again , then put it in gear and wait 60 secs. then turn the air on and do the same. then drive it and see if it goes away
hope this helped a little.