Just had engine rebuilt now when I press the gas the truck hesitates and sputters. If u pres the gas hard it cuts off or there is a pop that will come out of the carb sometimes but a pop always comes out the tailpipe when u press the gas hard. Other then that it starts fine idles fine but does hesitate and jerk when driving. It doesn't pop (backfire) when its cold and u gas it only once its warmed up. beBesides the engine rebuil I replaced fuel fuel pump, fuel filter n air filter. The accelerater pump seems to be working when the engine is off and I gas it. I'm at a loss please help