I installed the DR. D system on my 06 450 today. Man, its nice. I got the Spark arrestor and have a quiet core on the way. It seems that the overall noise level is a little less and bottom end power seems improved a hair as well. Fit and finish was perfect. I didnt have many hours on my stocker and I am not a real good rider so its hard to tell exact differences but I needed something with a S/A and a quiet option. For $450.00 for the whole system, it will be hard to beat. The dealership had one on their highly modded race bike(06 450) and also tried the FMF full mega bomb system. They said there really was much performance difference, maybe the FMF pulled alittle better on the top end. But for almost half the money, they really thought the DR. D was the way to go.