I am in the process of experimenting with exhaust systems on my MP3 500. I have a free flow exhaust on at the moment. I have found that the top end road speed and RPM has dropped considerably. At a flat-out top speed of only 70mph the engine top engine speed is now only 6000rpm. With the standard exhaust system I could trace a much higher road speed with engine speeds up to 7500rpm.
Has anyone else experienced this?