Okay, I believe what has happened is that the throttle position sensor is out of alignment. When I first began working on my turbo volvo 5 years ago, one of the first maintainance jobs I performed was cleaning the throttle body. Somehow, in the course of doing this, I got the TPS out of adjustment. The car would idle when it was cold but ran too high when warm. Therefore, I would try closing down the manual air bleed under the throttle body ( the black plastic set screw). When you come to a stop, the car would not have any air coming through this valve, and the idle air control over-compensates and the engine almost dies. Also, when cold, the car would idle too low. I finally decided I had messed something up. If you look in the 700/900 FAQ, you can find out how to re-calibrate the TPS. You need an allen wrench, a good ear, and about five minutes. It takes a little time to figure it out, but make sure you hear a "CLICK" when you barely move the throttle plate. If you don't hear this click, then you have found the problem. If you do hear the click, make sure the wiring is in good shape (the connector is on the back of the throttle body, but you know this). I put di-electric compound on my connectors just to be safe. It minimizes corrosion and helps to make better electrical contacts. Make sure you don't use conductive grease as this will allow a complete circuit between whatever the grease touches, hence switches will always be closed, hot wires could be touching grounds, etc. If everything is in order, check for vacuum leaks, but I am sure this is what you did.

I hope this helps.
Jeff