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Race Tune all the time. Better performance and fuel mileage than stock. Much more responsive. Not overly touchy at all. That said I have driven 10 second cars on the street and 7 second cars on the track so I might have a bit different view point than someone coming from a stock Focus.
PS - Stock M5 3.55 + 93 Oct Race Tune + CAI + Good Air + 1.9 60' = 12.9 1/4.
Definitely better gas mileage. Even punching the throttle now and then, I get 20-22MPG in the city. On the interstate I see about 28MPG. And on the highway, up the 34MPG! In fact, I can take off for the track, drive on the highway for 20 minutes, do 3 or 4 runs, come back, and have made over 20MPG even with the track runs!