2008 GMC Sierra 1500 5.3. I have spent a lot of money in this truck. I am riding on 38" Nittos and lifted about 10 inches total. I bought an itune and now it will not do anything but sit there. I bought the programmer to calibrate tire size with speedometer. little reading and research the following ...

I recently purchased my first itune programmer. I followed the directions to adjust my tire size for speedometer calibration. After reading the manual and little reseach, I wanted to make some custom changes. I plugged the itune in and started to backup original program like the manual said. now the ...