I haven't used a K&N in a naturally aspirated vehicle. However, after my experiences with them in turbo'd diesel, I won't have one. When I was truck shopping the last time, anything with a K&N was immediately dropped from consideration. In my experience, they're absolute garbage. Trash. Junk. Have I been unclear?
Seriously, I don't like them. Had one in a 7.3 PowerStroke truck, and it let dust through. My theory is that the turbo on the engine pulled a slight vacuum on the filter and it couldn't handle it, but I don't have the time/ equipment/ or care enough to put that theory to a scientific test. It did it straight out of the box. Cleaned and oiled it per the directions a couple of times, still did it. I've heard from several other folks with these engines that they've experienced the same thing. Your mileage may vary.