Wondered if anyone who had altered their wheel/tire sizes and noticed the speedo optimism increase (e.g. rolling diameter of 255/40/17's is 4.3% lower than stock 16" tires according to the calculator on the Miata web site) had tried one of these?
http://www.blackrobotics.com/index.htm
Looks like a well-thought out unit, I'll likely try it. Maybe Wayne could stock them if there's enough interest?