Originally Posted by Gen1dak
If you have a carb, it's been modified and no telling what the issue might be. If you're affectionately referring to the TBI as a carb, then I'd say your Hall Effect (aka distributor ignition pickup) is failing. They become more sensitive to heat once they begin to fail and will reset and function to varying degrees, becoming less reliable as they go. It's about $30, fits inside distributor, beneath rotor.
+1 for this answer. Common failure, with symptoms exactly as you described. And also, if you're playing the guessing game and changing parts, this is one of the cheapest, and easiest to change. It'll kill spark and injector pulse, by denying the computer a tach signal, and almost always be intermittent, becoming worse over time. Fixed my truck, and a couple like it. Also common on older GMs and Ford distributors.