my 94 chevy 2500 series 4x4 runs ok when cold, after that it runs terrible

until I floor it then it screams ? As long as the motor is climbing it is ok, until the feathering process, when it starts missing again terribly. I've installed a new distributor & rotor, temperature sensor, plug wires, fuel filter, the fuel pump is fine. Now, I don't know if it's electrical or a fuel problem. Please help Thanks