I have an 07 with DOD and I noticed no difference in the sound with the stock exhaust. When I added the Corsa sport cat back, there was a definite change in sound and there was even a kick in the truck when it changed from 4 to 8 cylinders. Mr. P is right about the DOD. I found it was only activated when I was coasting on a downhill. I disabled via hptuners and there is a definte difference in performance. Anyhow, none of this may make sense, but I figured I might as well chime in.