Hi guys,

I've been reading a lot of the posts and have been trying to learn more about these diesels. I just upgraded the exhaust on my '05 LLY -- cat back 4" mbrp and just last night I got a check engine light that appeared while driving on the freeway. I shut down the motor and restarted and the light went away. Tonight I was driving and all of the sudden I get the light again, but this time I tried to restart and the check engine light is still there -- OnStar ran a diagnostic and nothing showed up. I found out by testing that motor is pretty much out of power after 2500 rpm and it struggles to get to 3200rpm and this is unloaded. Has anyone experienced this with their LLY?:help:

only a cat back? You didn't remove the kitty? If you removed teh kitty then you will have EGR codes almost immediatly and it may/may not run like crap. Mine was one that did. There could be codes stored so I would head to the local parts store, most will scan it for free and find out if there are hiddne codes. the EGR ones are hidden until they get a certain amount and then it turns the SES on.

good luck