Sounds like a sticking IAC valve. IAC = intake air control, it modulates the amount of air going in at idle while the throttle plate is completely closed. It is very easy to remove and clean.

-Lance

Lance Kinley
CEG Webmaster
95SE, "Official CEG Beater"
Quaife, SVT parts, ST200 wheels, SS Y-pipe
I perceive you to be a stand-up, rational individual...