i have been running a k&n for about 2 yrs now. i did notce a proformace improvement from 1/2 throttle to full. and much quicker throttle responce.
gauze filters do not flow as much, but you greatly increase the surface area. when i was working at the cycle shop i had a chance to see a lot of their research.
i hated gause filters fo a long time but they are now all run but a prefilter is a must.