I have a 11gt and a Diablo in tune. My speedometer is off by 10mph at 85. I have adjusted the revolutions but its not working. I have 3.55 gears and 18 stock tires and wheels. I think I have the rev set at 740.. I have mess around with higher and lower.. But nothing seems to work, even Ford said everything is working right.. Still off 10... Can anyone help with this craziness.. Thanks