Every damned time I unplug my PCM my idle is whacked for about a weeks worth of start cycles. When stopping it will dip to about 500rpm and then jump back up to its set idle. It's been this way since I put headers and 58mm TB on 12 years ago. Doesn't matter if it's a different engine, tune or IAC motor. Just something I have to deal with.

 

sounds like the tune to me ..