Engine Idle surge after warm with no load on 1990 Chevrolet Corvette

The engine idle surges until I turn on the air conditioner.. No vacuum leaks found.. what could be the problem.. THought might be head gasket, checked the block for leaks and nothing... In need of help..

1 answer
Check you ignition wires ASAP, I have replaced wires on Vettes of this era for this very problem which is a hunting or surging idle, with out any load that goes away with the A/C on.

here are some shops:

https://repairpal.com/directory?address=76052&car_brand_names=Chevrolet