I was driving down the highway when my 91 Camaro RS shut off. After letting it sit for a few minutes it started back. I opened the gas cap and lot of "air" was released and the car shut off. Replaced gas cap, restarted no problem. Got further down the road, it shut off again. Restarted, removed gas cap, air released car shut off. Any ideas?

 

I'd guess that the gas cap is coincidence. I'd look at trying a new ignition module located inside the distributor under the rotor button. The ignition module gets hot, and fails (since it's electronic). When it cools, the cra restarts and runs fine, until it gets hot again.

But I'd change your fuel filter as well, if it hasn't been done in the last year or 2.