K&N filter, bah I'm not spending $36 for 1hp, heh
with my airbox cut open like that, it lets the engine suck in enough air. Believe me, my engine has some MAD vaccuum, and the Fram filter can't suppress it all. I got my hand sucked up into the AFM once!
I won't go with an open air filement either, I hear they make a whistling noise, I don't want that. With my current setup, the engine growls at WOT
I'm looking into getting a RabidChimp intake soon to replace that crappy plastic, then I might build a custom carbon fiber airbox w/ holes