Bad IAC valve or throttle position sensor come to mind. I had this same problem for a while and I just simply reset the computer and it fixed it. When my SVT did it it was very intermitent.

Been going for a month w/o any problems. If they havent reset the comp. ask them to. Or just take the neg. battery cable off yourself and let it sit for 15-30 min. Worked for me smile

-neal

99 SVT...modified
96 GL....the beater
"I live my life a quarter mile at a time. For those 14 to 15 seconds, 16 if I get tire spin, or get a bad jump, or possibly if I have a friend in the car, I'm free."