I have a 99 quad cab 5.2L that is sporting 255/75 R16 instead of the stock 225/75 R16. The previous owner who put on these larger tires did nothing about reconfiguring the onboard computer, thus my fuel economy readout is inaccurate and I don't know how to refigure it without popping forty bucks at the dealer for them to reconfigure the computer. Also, is my speedometer still accurate? What about my odometer? What else could this affect?