Duramax Lifetime Supporter
Join Date: Oct 2016
Location: Maurice, LA
sounds like a sticky EGR valve, and yes you have an EGR valve and cooler. The cooler is necessary to cool the hot exhaust gasses being pumped back into the engine.
First Id check the connection and/or the wiring to the valve.
You can try cleaning the valve but if that does not work you can replace it. Not too difficult. Removing he EGR Cooler is another ball of wax.
2008 Silverado 2500HD CCSB LTZ Diesel
FASS 95 Lift Pump (with Baldwin filters), Edge Insight CTS Monitor on a Windshield Mount, Nicktane Fuel Filter Adapter w/ CAT 306-9199 UHE tertiary fuel filter, Bilstein 5100 Stock Height, Bushwacker Bed Rail Caps, AMP Research Bedstep, Fumoto oil drain valve, Dorman PS Oil cooler, Pioneer AVIC 7200NEX GPS/Stereo, Air Lift LoadLifter 5000 Air Bags.