Unbroken and TMac are on point. I've run the ZFG Auto Octane Tune for about 6 months. Typical driving. A lot of city driving, Two trips to Washington DC, few runs on the Blueriidge kind of thing Shortly after tune instal mileage went down about 2 mpg, totally on me. Checking out the new found HP and having fun. Now that the newness has worn off, mileage is where it was before. Around town or on a trip you will never know it's tuned. TMac's turbo thread noted this platform mostly lives below 2,000 rpm. At that level, shifting is smooth as silk, much better than stock for both upshifts and down shifts. The noticeable difference is when you either leave it in normal mode or sport mode and get aggressive with the go peddle. At that point, plan your moves well in advance....and hang on!