[snakebittexan]

I recently installed a phenolic spacer and I've had no furthur such issues. For a test try some Lucas Fuel Conditioner in your tank. If that solves your problem it's probably the fuel boiling in the bowls (thanks to our corn/fuel), assuming you have a carberator. As an additional benefit I've notice some performance benefits due to the spacer.
If your drive the next day was in the AM (cooler) vs. afternoon that may be why your issue improved.