[luke0490]

Hey guys my buddy has a 2005 chevy duramax. He has had the truck for a couple of years and has kept it bone stock. He just replaced the stock exhaust with an 4 " mbrp exhaust that does not use the cat. As soon as he changed it his ses light came on and he is not feeling the same power out of it. The truck feels sluggish and does not have the same power it had when it was stock. We checked the codes and they came back with p0299,p0401, and p0404. I know these deal with the egr valve. My question is would the exhaust cause these codes and how can we correct the problem. Thanks guys...