most power. firmer shifts. change the rev limiter, change the governor speed. mines set 210 mph. like im ever gonna hit that. haha its mainly for more power and better shifts. you take it all out of the box. plug it in to your obdII port. plug the other end of the wire to the controller. answer a few basic questions. press lvl1 lvl2 or lvl3. i did 3 once. dont wanna pay for 91oct though. but lvl2 is what we mostly use. cause lvl1 is just firmer shifts. then you can keep an eye out on vidals. its kinda fun to watch mpg. go from 11 cruising to 4 when you floor it. haha