Thought it would give better gas mileage, but really haven't seen it. Easy to follow directions and updates installed. It may growl a little more, but I also installed a k&n air filter at the same time and it was supposed to be a boost and still haven't seen any boost with either! So maybe if your foot is always in the gas it may save some, but the Tundra 6 speed is a shift monster and I did notice shifting differences but no change in my.
Bought it cause I put 35's on my Tundra and I was about 5mph off comparing to GPS. Also noticed shift points were off along with gas mileage. This calibrator not only allows you to fine tune the speedometer but it also brings the shift points back to factory settings. I am now back to 18+mpg on highway and 13-14 aound town and I am heavy on the right foot. Easy install, just make sure to zip tie to prevent rattles behind the dash. Highly recommend.