I have an 04.5 lly duramax and have had problems with fuel knock and rough idling this problem greatly increases with use of chips or programmers. Right now I am unable to run anything sort or programmer due to these conditions. The truck has been in the shop several times but GM is yet to fix the problem or to find what the problem even is. GM has supposedely updated the truck with the new computer program. The problem I am having now is when the motor is around 180 is a getting a loud rattle or fuel knock and when the truck is in drive with my foot on the brake it shakes and sounds like the motor is skipping.

Any suggestions appreciated because my dealer obviously can't find the problem.