man this topic is old.........penfold is right, if you not planning on new exhaust and/or jetting, maybe a K&N filter is not as effective...in other words if your bike is mostly stock might as well leave it that way K&N aint gonna help. i personally have only seen success with the K&N's (00 with full akra exhaust and jetted) and they are a superior filter. other than that i dont know about other after market filters....im sure they are good as well.