step to more total power...if you have a total package. Just increasing size alone could result in a loss of power, or specifically, less torque (low end power) if things aren't planned out properly.

The stock S4 head and the stock S4 intake manifold are already matched pretty well...and there is some improvement for opening them up...but not to the extent that the NA heads are opened....aproximately 30% larger.

The enclosed picture shows the throttle body difference between the RS4 (pictured) and the S4. The I.D. of the sleeve is about the same as the O.D. of the S4, while the O.D. of the sleeve would represent the RS4.

But....size alone is not the biggest issue. Making sure that the software is right for the mating of your engine/turbo/exhaust package is more important.

I wouldn't suggest anyone modify their heads/cams/intake without the software to go with it.

Whomever you use....Revo, GIAC, APR, OCT, etc., all of these companies are striving to work outside of the box that Audi designed, and with great success! Gains that can reliabley double the factory quoted horsepower figure is pretty substantial!

Don Istook