The MR's have shorter gearing for racing/keeping it in boost. The MR's (actually all 2nd gen GTO's) have shorter gearing than the US bound 6 speed 3000GT/Stealths had. The US 3000GT 6 speed was geared to where it could do a theoretical 245 mph. The JDM GTO 6 speed was limited to "only" 190 if memory serves correct.