what is the desired idle rpm?
sounds like the egr needs cleaning or replaced,it controls the idle,it should idle around 650 to 1,000 rpm.it may also have a bad throttle position sensor,or idle air control,both located on throttle body.
Search Chevrolet Silverado 2500HD Questions
Chevrolet Silverado 2500HD Experts
Related Models For Sale
Used Cars For Sale