I waited a long time to buy this, too long actually. Since I have gotten the Evolution, I have kept it in Level 2 (towing mode) and boy is there a big difference. I can now spin the tires on my '05 4.6L V8. A definite power increase. I have seen a slight increase in mileage, only about .3-.4, but that's because I drive all city and can't keep my foot out of it. Can't wait to try Level 3 and take a road trip on the highway as well. Overall great customer service by Edge and Autoanything!