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  1. 2005-2010 Mustang GT Tech
    I had 4:10's put in the rear end the other day. Today I changed the tune using my Xcal2 to 4:10 gears. I pulled out my GPS to check the speedometer and its way off, Going 45MPH my speedo says Im going 95, its off big time. I noticed I can change the tire rev, but I didnt, I cant find the...