Welcome to the site.
Plenty of posts in this site regarding similar symptoms. Have seen anything from bad EGR, to poor fuel pressure, to a bad distributor. A sloppy distirbutor can cause this problem at low rpm. You could also have a blockage in the fuel system return line. Blockage of the exhaust (bad cat) can also cause poor low rpm performance. Bad O2 sensor that is not in closed loop could also be running the engine at full rich conditions that could kill the engine at low rpm's.
Gonna have to run some tests to isolate the problem.
You have thrown parts at it already. Did the truck give you any codes that would indicate or lead you to believe that the replacement of the above parts were necessary?