95 k1500 stalling out

my 95 4.3 5 speed is giving me a bad time right now. it is getting pretty cold here in nebraska this time of year and the beater starts up fine and runs fine for a few minutes, then starts feeling like it isnt getting fuel or possibly spark. this all happens while the motor is still cold. it will buck really bad on the road and lose most of it's power and will stall out if i am at a red light and not helping it with the gas pedal. it always fires right back up again, although it only runs fine for a second or two before sputtering again. you can feel it coming on if it is sitting in the driveway warming up in the morning. it will run fine for a few minutes, then the rpm's will start fluctuating up and down a little and the fluctuations become wider and wider rpm gaps untill it sputters out completely.

It does this until the engine is fully warmed up and then it runs fine after that. if i let the engine get too cold after killing it to go into a store or something, it will have the problem again when i start it up and it goes away again once the engine is fully warmed up.

i took it to a shop to get the fuel pressure checked and they said it was totally normal and of course never acted up when they were running it.

any ideas guys?

first thing u gotta do is go buy a pressure tester and hook it up to ur service port.... duplicate the problem with the pressure tester on it... then go from there...