Why does my cutlass rev up so high without pressing the gas pedal? on 1999 Oldsmobile Cutlass

Sometimes it does this when I first start the car. I took it to my car repair man and let him have it for about a week and let him drive it and it didn't rev up on him. He also tried to hook it up to get a code and it didn't give one. PLEASE HELP!

kind of sounds like an intermintent vacum leak.
thanks, I'll have my repair guy check it out..