I read an interesting review not long ago where a dual Leo Vince was tested against a cheap danmoto exhaust on a GSXR1000. They tested them out on the track and on a dyno. There was no detected difference in performance between the two. The differences were that the danmoto cost a couple of hundred dollars and the leo vince over a grand, and the danmoto was described as being built of quality parts, but just not as "pretty" as the name brand.