GMC 3500 /G Stalling when hot

Hi, I hope someone can help me on this. I have a GMC 3500 box truck. 102,000 mi. I have had a new fuel pump, battery, plugs, wires, rotor, disturber cap installed. No scanner codes and shows a good data stream. Injectors show a good spray pattern.
Problem, after about eight hours of stop & go driving the motor begins to stall and idles rough. To keep it running I need to have one foot on the break and one on the gas peddle.
After it sets for 4 to 5 hours this trucks runs great. :banghead:
Thanks
Bill