There was a K&N thread a few weeks ago, try a search, I'm sure you'll find everything you want. Mostly it said you get a touch of gain [at the cost of a little filtration], but nothing too substantial. Some love it, and say you can feel the difference, but mostly I'd guess it depends on how filthy the filter you're replacing is. Look into TVT, Needswings, etc. for options to upgrade your Crossfire.

dh