My 72 Camaro with a TPI 350 L98 when cold runs great then when it warns up on a warm day it seems to lose power my son noticed while following me the other day that when i would get on the gas that fuel would pour out the vent hose that is routed from the top of the tank forward and then under to the rear and is visable from behind. Anyone have a clue?

 

Ensure a vented gas cap is installed, allows air into tank, but not out, and plug the vent hose.
Or, run the hose to the charcoal canister for venting, just as if the TPI were installed on its original design.