Wow! I really fell a slight gain in performance with the new Green Brand Air Filter. I installed it myself on my 2002 S6 Avant and can feel a slight improvement in acceleration. It has better flow than a k&N because of its low usage of rubber around the screen ,therefore giving it more filter area than a K&N around the edges. I highly recommend them. When the car downshifts in tip mode you feel a lot less drag on the motor because of the free flowing intake. The cheapest upgrade available at 68 bucks.