I'm surprised you are asking this question since you are a regular poster ..
the fuel pump must have the fuel test proceedure done..this with your limited testing appears to be the fuel pump check valve..but what is the pressure with the key on engine off and the pump is running..?also with the engine running ? sounds like pump does not have the correct pressure when engine is running ...
check for proper ground and feed voltage at pump with pump on ..
you also stated spraying carb cleaner to check for vacuum leaks..this is good for cleaning metal only..this product over time destroys gaskets and rubber compounds..