I was trying to shy away from that box because of everyone saying it messes up pretty much everything but the speedo. I am going to make an attempt at calibrating it myself, I have found several sites on how to do it, so I figure I will attempt it and if it doesn't work I believe I have a back up, or will just get another one. From what I have read and seen, I am hoping it will be as simple as adjusting the spring. However there is a magnet in there that I may need an electromagnet for if the spring wont adjust far enough. If anyone has any one can shed some light on any of this and either confirm or discredit it please speak up! If all goes as easy or hard as I believe and I can do it, I will do a write up on it so other people can try.