Two suggestions:
1. adjust valves. if you have a tight one or two they will expand when hot on a trip and not seal as well as when cool.
2. Treat your tank to a good dose of Biocide in case there is bacteria clogging your tank screen.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.