I recently purchased a '99 C2 with 65K miles. When I start it with the engine completely cold, it will instantly rev to 4K+ rpm's and immediately return to normal idle. When the car is warm, even after sitting for some time, it starts normally. Also, it has a rough idle at operating temp. Any suggestions on what it could be? Thank you.

 

I would start with a MAF cleaning (because it's simple and could cause your symptoms) and go from there.