Does anyone know why my diablo tuner will not correct my Speedo. I have a 2001 GT and I have 3.90 gears and I set it correct and install but the speedo is still off 10 MPH. I followed the instructions for installing the tune but still no good. any advise??? Also I need to retard the time a few degrees but not sure how much or what to set it at. I'm running a MMR 850 mod with 10.5 to 1 comp. Thanks