Cummins ISC cough

Truck .. 2005 Freightliner M2 with Cummins 8.3L ISC. No codes, live scan looks normal except pedal position 1 flickers sometimes.
Symptom .. low rpm (1000-1400) cough with belch of black smoke from exhaust when using light acceleration. Worse if loaded and starting out going up a hill.
I feel like its a pedal position sensor any advice appreciated.
Thanks

 

It started doing this after a oil change to rottela T. I will check but i didnt think this truck had a egr.
It runs rough like its dropped a cylinder or two for an instant. Or like the grid heater kicked on in cold weather.
I will have to check on the hours on the engine the truck only has 152000 miles.

 

Fuel Filters were pretty dirty, adjusted the valves all were pretty loose. Finnally just started disconecting injectors till the poping stopped. The problem was #3 injector electricaly is fine no code, but either the transfer tube or nozzle was dirty could have been sticking who knows but I disassembled the nozzle and cleaned them up reassembled injector. Truck runs fine thanks goodysnap happy Easter to you and your familly!!