Truck has 188,000 on factory everything. I have a small tuner, maybe 85 hp. 6 position chip. Truck has a studder at lower RPM and about 2000 RPM will smooth out. Gets worse in higher elevation. Sound like tired Injectors? That's all I can think it would be.

 

Could be anything, you need to scan it and test things to find out if its the injectors.

 

test the hpop

 

How many miles are on your oil? Over time oil brakes down in the Huey injection system and will cause studders