My stock 95 LT1 camaro with 100,000 miles runs pretty well except when it has been running for a while, shut off for about 10 to 15 minutes, and restarted. It idles fine, starts ok but, when given gas, it stumbles, and backfires in the intake a bit. It doesn't have full power for about 1 minute of driving. Then everything clears out and it runs great. I noticed a bit of a cold start problem this winter and actually had to pump the accellerator to start it. I don't know if the two are related or not. Thanks

 

Vaporlock can only happen when the pump has to suck fuel out of the tank like on carbed engines with the pump mounted to the block, your car has a submerged(in gad) fuel pump.

 

Still could be a fuel problem, though. You might have a leaky injector or a bad fuel pressure regulator.