Yeah I had a K&N Filter for a two weeks but it made my gas mileage go from 370km a tank to 270 a tank(no joke). So needless to say I got rid of it quick. One thing I just did to my car is install Accell 8.8mm ignition wires with Bosch Platinum spark plugs and I really noticed the car being smoother at higher rpms. Let me know if you find out any other power tricks.