Duramax LLY MBRP 4" Cat-Back Exhaust

The Duramax LLY has a lot of restrictions within its exhaust system. The downpipe is the most restrictive unit, which is why we always recommend upgrading that with MBRP's 3" downpipe. But the cat-back portion of the exhaust system is also restrictive as well meaning you can both increase performance and improve engine health through reduced EGTs with a cat-back upgrade.

 

This exhaust system for the LLY from MBRP is a 4" aluminum cat-back exhaust with a muffler. It's the most budget friendly exhaust upgrade tailored specifically towards the LLY. The aluminum material combined with the muffler will reduce virtually all drone that you tend to get with steel and straight-piped exhausts. 

 

Now, combining the exhaust with a downpipe (which we recommend) is going to run you around $600 in total. The alternative option is to purchase an LB7 4" exhaust which runs about half the cost and is a turbo-back system. This exhaust will bolt up to all 2004 and 2005 models, but does not include a catalytic converter so it is only within emissions regulations on LLY's that did not come with a cat from the factory.