I just bought a DRZ 400 S, and want to perform a few basic mods, based on the collective experiences and positive outcomes I've read on his forum. I'm and older guy, and familiar with Supertrapp exhaust systems (I used these a lot on big-bore 4 strokes back in the 80's). I like the diffuser disc design, allowing for adjustment of exhaust flow and back-pressure allowing for shifting the power-band around an RPM range by adding/subtracting discs (and they sound great). I have not seen any posts regarding this type of exhaust, and would love to hear of anyone using one. I'm also curious if anyone has tuned their post-mods using an EGA to quantify the actual stoichiometric ratio. It would be the only way to know if the tune is actually at, or close to an optimal stoichiometric A/F ratio of 14.7:1.