This is definetly a temperature related, heat soak type problem. It only happens when the truck is hot and then parked for a period of time 5-20 minutes then started again. It then runs rough, stalling and bucking except if pedal is punched to floor, then it starts again as soon as pedal comes back off floor. It does this for 2-3 minutes and then runs fine untill shut off for that period of time. When the engine is completely cold it starts and runs fine perfectly and is perfect after intial 2-3 minutes on a hot motor that has set for 5-20 minutes.