ive made some searches and i am still unsure as far as tunes are concerned. right now my car recently underwent the 4.10 gear upgrade and i want to recalibrate the speedo. my dealer charges $100 to recalibrate it but ive heard that certain "tunes" can do more than simply recalibrate the speedometer. my question is, are there any tunes in the price range of $100 that can fix my speedo and would be worth more than going to the dealer? keep in mind i have flowmaster 40s and the mustangtuning o/r x in my closet ready to be installed as well as a k&n on order. would the tune thing be better, and if so why?