A co worker has an '05 LLY, and is looking at an exhaust system(turbo back). He'd like the Flowmaster, but there's no listing. I was telling him to try the Summit stainless. Any other good ones to tell him about?

lots around here have got MBRP, I like it lots. Some have the system from Kennedy Diesel.

There are a ton of threads on different exhausts, browse the old performance forum, or search...
New exhaust threads go here:

Fuel System & Air Upgrades

Discuss upgrades to the Duramax fuel system and air system. Bigger turbochargers, more turbo chargers, air boxes, exhaust systems, and fuel pumps all go here.