My friend just bought an 06 Denali XL. It has the 6.0. With that being said, it has a real nice throaty sound to it. My 06 Yukon with the 5.3 is very quiet. I looked under his Denali, and the exhaust is 100% stock; however, he has dual pipes instead of the collector, and then it feeds into the muffler and comes out in one pipe, just like my Yukon. What is the point of the dual exhaust, if it goes into one muffler??? Does it give it more breathing room? I'm tempted to put a similar design on mine if it gives me a little more power. Basically I like the sound as it is throatier then mine, but not aftermarket loud. Any info?