The difference is amazing. I took my track car to the dyno today to hone the fuel mixtures prior to this weekend's track event (it is 30 deg warmer than the last event) and the car felt like a lame dog in comparison. This is the same track car I drove just to the AM dealership to test driving an AM Vantage V8 and it spoiled that test completely. Exhaust and ECU definitely take the car to a whole different level.