[JCsGTPT]

K&N drop in air filter, part # 33-2153. Should be around $30 or so. If you have Autozones in your area they carry it. This is a reuseable filter so don't forget what is called the Recharging kit for $10-15. I haven't checked the mileage interval yet but every so often you have to clean it and re-oil it.

Also, many do what's called the air box modification to improve the airflow even more. I have done it and it is very simple and takes less than an hour even for a novice. It entails removing a white ring silencer and cutting back the snorkel that feeds into the airbox. If interested, you can search on it in the forums for more detailed instruction.