If your going to race MX and there's any sort of dust involved then you would run a million miles from a K & N filter....they do not stop dust period.....all they do it make more horsepower as they don't restrict airflow very much......engine rebuilds are dearer than a pain in the arse oiled foam filter. I have also seen the results of foam filters that have not been oiled....not pretty either. Unfortunately the best way is the dirtiest way, but hey, rubber gloves are cheap.
