I've taken that off once and it only made the engine much louder and, to my foot, impacted performance. Needless to say, I put it back in.

Save your $$$ on a K&N. You'll get the exact same thing buying a Spectre filter. Reusable, washable...Oil it and you're set. They come ready to drop in. I always buy these over K&N simply because they cost less, are the same quality and perform the same. Look em up...Spectre.