The truck is an 89 7.3 IDI, newer IP with somewhere between 20-30k, new return lines, check valve in filter head, cleaned and repaired FSV. Occassionally when hot and idling, the engine will run rough and smoke, almost like an air intrusion issue. Fine when engine is cold. Runs great when moving, plently of power, issue is only at warm idle. Put clear Pvc hose in the supply line going to the IP, no air bubbles. When I ease into the thotle, it smoothes out some, but still isn't right. I can quickly give it throttle, and it sounds almost like a lifter ticking, imagine its an injector making the noise though. The trucks done this for the last 20k miles, with the old worn IP and the new IP, tried adjusting the timing, never had any effect. Some injectors were changed by the previous owner, Is there anything I should try before finding the bad injector and replacing it with a new Delphi one?

 

Sounds like injectors to me man.

 

OK, thanks.