It may be that the ignition coil is going south. I say this because the problem sound heat related and not so much fuel. If you are back fireing and I assume it is through the tail pipe and not the intake.then the fuel is being loaded into the cylenders without spark and when the coil cools the spark comes back.
also the ignition system under the cap mabey going bad.When a fuelpump goes bad it almost allway goes bad @ once.
hope this helped