My 1992 STS has a problem now where I have to put my foot on the gas (the other on the brake) to keep it idling. It will stall out at low speeds (during a turn) or when stopped.
On the highway, it drives perfectly.
When it does stall, the lights get dim and the voltage indicator on the dash drops, but then goes back up to 13.6v when on the highway. Of course, low voltage could just be a momentary product of stalling.
I've done some searching and did read up on grounding, ISC, and distributor. The fact that its fine on the highway and refuses to idle makes me think its something other than an ignition issue.