I have the same w/ my M2 but I don't want to spend the money to have the computer re-calib'ed, yea, cheap I know. Use the yard sticks for a set amount, say, 10 mi.s, and compare to your dash odom. Figure the percentage, my is 2% off, or .2 more on the odom in 10mi.s, 2 in 100, 20 in 100, 2000...