I sure as hell would if he is having all the issues be described. Im confused though. You said you swapped a pretuned ecm in and it ran fine thats why you are ruling out hard parts. Why didnt you just keep that ecm in the truck? It would have had to been tuned for your truck to begin with so where did it go? Like tom said if its throwing codes then post it up let us know whats its doing. We cant help with the info we have.
Load a stock tune with LBZ FPR scaling and see if it runs fine, it says "barely running" with no real description....
A stock LB7 file with the correct scaling to idle smoothly, in a sac 45 injector truck will run about like a "tow tune" in a stock injector truck.
If not then there is other issues that need to be looked into. As far as codes what are they? Generally codes cant point you in the right direction of the issue.