904 differences

Totally agree with Trailbeast. With that much power it most likely wont last real long shifting that smooth. Smooth shifts are for Granny's grocery getter or something you don't plan on running hard. Not saying you need to make it slam the gears, just needs to be firm. As for the speedo, do you have or know someone that has a GPS you can use to check the speedometer with? That's how I do them. It's more accurate than pacing with someone, and easier.