KR57... The blow by is filtered inside the valve cover under the breather valve. But it isnt a very efficient filter element.

 

Tests like that is one of the reasons I quit using K & N's years ago. I kept finding dust in the intakes on about all the machines I had them on. Test after test shows them as being the worst in filtration. Horse power gains are minimal at best. Guess they may be alright in a clean street environment if you don't put many miles on. Use 'em if you want, just not on my machines.