I installed a K & N filter in my wifes C230 kompressor engine after we bought it and didn't notice any differences. Several weeks passed and I reinstalled the oem filter to see if I could feel a decrease in hp (of which I think is easier to do than a slight increase) and I immediately noticed a part throttle decrease in power. The mid range or part throttle response seemed softer with the oem filter, so I reinstalled the K & N and immediately the engine felt more responsive in the mid range again.

One thing I can't tell the difference between the 2 filters is full throttle power. It would make sense that the K & N would breathe better at high RPM but my calculated ass can't tell any difference. I love the K & N's for their longevity and the mid range power increase in her car.

Dale