I have an 01 GMC Z71 that has been lifted. I am running 35s and next week I am getting 4.56s installed. My calculations put me with the speedo reading high after the gear install. (compared to 265/75/16s with 3.73s) What is the cheapest way to access the computer and make these changes? I really don't want to spend 300 bucks on a hand held tuner just to do this. I didn't realize at first that some of these tuners are VIN locked so once you use it you own it.