I have a 2006 GMC Sierra Vmax. Its the 1500 regular duty, not heavy duty. Its a ccsb, witht the 5.5' bed. The LQ9 has a TR224-112 cam, K&N cai and obx headers with dummy cats. We had a magnaflow exhaust system for a 05 denali laying around the shop. So, we tweaked it a lil bit to make it fit. But it sounds like crap! Inside the cab drones terribly and just doesnt sound that good??? Outside the truck, it sounds alright, just not that deep smooth sound magnaflows are famous for. More of a higher pitched raspy sound. I don't know if its because thd case length or the overall design being for a different vehicle. The tip is a 4" that exits behind the rear wheel, and I love the way it looks. The tailpipe section doesnt exactly fit perfectly, of course. So, does magnaflow currently offer a catback for an 06 ccsb with a 6.0? Does it have the smooth deep sound? Or this more raspy sound Im getting? Does if drone? I can live with the more raspy sound, as it sounds pretty good outside, but the drone and sound inside the cab is terrible!

 

I'll trade you my 18" 2.5" dual in/out magnaflow. It will still drone like crazy, but it has that nice deep tone you are looking for. I think I am about to cut my tailpipes off to change the tone.

 

I say it's the headers and dummy cats causing the sound quality.

denali system
http://www.magnaflow.com/02product/s...ne=all&id=6028

truck system
http://www.magnaflow.com/02product/s...ne=all&id=5761

truck system has resonators in front of the muffler regardless of whether it would be single or dual tailpipes.

my truck had a terrible drone as well after the headers were put on. I put a resonator in front of the muffler and it sounds perfect now. but mine has a single pipe in front of the muffler, yours likely has 2 so not so easy to do.