I have a 2000 Chevy Silverado Extended Cab 4x4 and when you first start it it starts missing and when you press the gas pedal the motor will cut out . You can drive it down the road and the motor will finally start running the way it's suppose to . But if you cut it off it will start doing the same thing all over again. I have put a new fuel pump and new fuel filter on it but still the same thing. Does anyone have any ideas what it might be?

 

I'm not sure if you got this figured out yet, but it seems I had the same issue. When I first started my truck, it would run rough, miss firing a bunch, until it got warmed up. The colder it was in the morning, the worse is ran. I found that I had a vacuum leak due to the intake manifold gasket. Air would leak in until the engine got warm enough for the gasket to expand and seal up. I hope this helps some.