i bought a cheap used 4" by 9" K&N filter from someone on these boards on ebay. i currently used a drop in K&N with the stock airbox, no silencer, and an intake tube similar to the straight shot. i put this new, much larger, filter on 2 days ago with no airbox. i was surprised that i really did feel a nice increase in pull, revs quicker, and is much more responsive. seems to pull harder too. im very impressed for the little money i spent (about 20 shipped). highly reccomended. i have an adapter on its way now but i strapped it onto the lip on the housing for right now. it is large though. my intake tube is shortened by about 3 inches, and it was still snug in there.