I had a Jackson Racing supercharger on my K20 CSX Type - s. 11lbs of boost and made power all the way to 8200.Just experience with the superchargers and turbochargers in the Miata and a friend's Exige, the turbo cars fit the nature better and were faster. Superchargers have the parasitic loss and while they make great torque down low, they just all seem to run out of oomph by the time a smallish 4 banger is starting to really rev. I guess they make more sense on big V8's, or at least augmented by a turbocharger for the upper range, like Volvo is doing.