Late to game here but I ran K & N filters for 30 years, but have since gone back to Donaldson paper. Where I live (southwest desert) we have very fine dust, not much sand. When it's really dry and disturbed I call it "moon dust", think very fine flour, gets into even the best sealed buildings. Turns out it was going through the K & N as well. While it never caused me engine issues, I didn't like running my finger in the intake tube and seeing that dust coating. High quality paper has stopped the dust. I'm not knocking K & N, they are great in the right climate, but just not for me anymore.