if you run a straight exhaust you will throw codes unless you get the EGR blocker plate and finger stick or boost stick. I have a LB7, so I don't know a whole lot about this, but check these threads out: Boost Stick EGR Blocker Plate
I am getting ready to cut my muffler out and go straight pipe, but I have no experience with aftermarket exhaust. Just remember, you don't have to go with a name brand exhaust to have a good one. Most of the time they just empty your pockets when you could have spent less. I'm not going to point out name brands, I will let you figure some of that out by yourself.
__________________ 2004 GMC 2500HD D/A CC Carbon Metallic w/ LB7
4" turbo back MBRP exhaust
TST Powermax Programmer, Diablosport Predator
285/75-16 BFG T/A KOs, Eagle Alloys Series 187
Clifford 2 way remote start, High Idle, Bilsteins
Extang Classic Platinum Tonneau Cover
AFE Magnum Force Stage 2 Proguard 7 intake Kennedy Diesel Merchant Automotive My Photos | 
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