runs bad
 

ok have a 1996 k3500 dually/6.5 turbo. starts ok when cold,then after driving around block a few times it tries to shut down and goes into just idle maybe. no throdle.. put new primer pump , filter, tank unit. now the tach quit after getting alt rebuilt. has a black pmd on it. now comes the good part. have a 96 gmc k2500 sub with same motor that runs like a top. which has a off mounted pmd (grey) , put it on other truck and it want start.change back and both run. how does the tack affect the ecm. going to swap out engines after my broken leg heals then junk sub . but right now need my dually going. been a cummings mechanic for 15 yrs. hard to find a dodge/ cummings, so i had to get this one. any help would be useful right now