The truck is a 03 chevy 2500HD 4x4 with the 6.0l around 100k miles. Seems to sputter and not want to start on the first try sometimes like it is not getting enough fuel and if I do not shut it off in gear it will "Diesel". Also since this issue has started the truck seems to be underpowered. Has not thrown any codes yet. I was thinking possibly the throttle position sensor or maybe the gas tank is not venting right? Any help or advise would be great thanks

 

check your injector O-rings. I've seen the same issue with a little 4 cyl. It is hard to start and lacks a lot of power. Also check the continuity in you wire leeds.

 

I have two of these trucks and have had the same problem,my fix was the prime button has rings under when you remove the 3 screws to the button.replace it, the c ring will still be ok so don't

trouble your self finding
one of those.