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Discussion Starter · #1 ·
Hi my name is Scott and i am new to this site. I have a 2005 gmc 2500hd with the LLY duramax. i recently put my cat back on because i am tried of not being able to smog my truck legally and even with the cat back on i am throwing the egr insufficient flow code when i put the programmer back to stock

Current mods on my truck are: LBZ mouthpiece, PPE exhaust manifolds with functioning y pipes, PPE axellerator tuner, 3 in down pipe from turbo to cat, 4 in cat back exhaust, and a 6 in lift kit on 35 in tires.

Is the bigger downpipe throwing that code or is it something else?

Thanks in advance for any help, and FYI i live in California so being able to smog the truck is a big concern for me.
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