these are extreme conditions, but you'll find many people complaining about k&n and letting to much dirt through.
K&N Filters let in way too much dirt. - Raptor Forums: Yamaha Raptor Forums
K&N Filters let in way too much dirt. - Page 3 - Modded Yamaha Raptor Forums
K&N Air filters Vs Foam - Yamaha Rhino Forum - Rhino Forums.net
I've since switched to UNI foam filters on my modded cars. those are great, but for my 370Z, I'm sticking with OEM Paper.