I have a 2000 GMC 1500 with the 5.3 4x4. When its warmed up, it doesnt like to start till i pump the gas a couple times, also will die when idling. i get code P0300 i have new spark plugs and ignition wires and new fuel pump and filter. i can hear all the injectors opening and closing. I get a little white smoke out of one of my pipes. I have dual exhaust.