Ive put on 9 exhaust on my SD trucks as well as Duramaxes over the years. MBRP, DPPI, Banks, Magna-Flow, I just installed a turbo back Cat delete cool dual system from MBRP. This one is my favorite. Get the 3 1/2 down pipe vs the 4" this way you will not have to do any firewall modifications. Fits perfectly, quality parts, and sounds excellent. Almost like stock when driving normal with windows up and at 2/3 throttle has a nice big block sound. Outside the cab others will hear a nice whistle of the turbo out the pipes. This system is an excellent system with out the droan that I have had on others at freeway speeds. Buck on here will possibly help you out or try
www.innovativediesel.com ask for eric, or Ted. They have SCT tuners, and all the stuff at hand. Good Luck Jeff