1994 dodge ram 1500 runs good then starts backfiring threw the carb and want go like it's out of time or running out of gas. It does that for about a minute then starts running good again for a few minutes then starts running bad again. Put twin pipes on it new plug wires, dis cap, rotor, and have put new intake gaskets on it also fuel pump. Also vent door will close when I give it more gas and it will open back up when I let off. What do I do?