I have a 1984 Corvette with a 4 + 3 transmission. I purchased it earlier this year. It had 100K miles. One day I started it and the rpms fluctuated between 7 and 13. I had to keep my foot on the gas to keep it cranked and moving. If I come to a light it will cut off. I have changed out sensors and I was told to buy a new computer. Nothing works? Any suggestions. I

 

Welcome to CF.
Hang in there, I know the answer to this is commin'.
I know a couple of guys here, that can nail this one.

 

Sounds like a vacuum leak on the upper plenum. Cross-fires were notorious for sucking in the upper plenum gasket in behind the throttle bodies. Try spraying a little carb spray along the back of the plenum and around the intake to see if idle stabilizes. Don't go crazy with the spray, though. [8D]