Everyone is different in how they have done theirs. I ran 2.5 " with no resonator and a fully welded high flow muffler. Less loud in the cab now than the old stock system (which had a small hole in the muffler) and throaty outside when standing behind it. The shop ran it straight out the back with no down turn. A bit of soot building up on the chrome bumper but nothing that couldn't be taken off with some work. I did notice a large power increase but it's still no rocket. The biggest thing I noticed was that my large super heavy 33 " FC II tires feel like the stocker 30's the truck came with. I imagine with lighter tread, it would feel even better. Next step for me is a mandrel bent tube from the air box to the turbo to replace the rubber accordion one that is there. Probably won't make much difference in power but I love the sound of a good intake. <img src="/forums/images/graemlins/cheers.gif" alt="" />