There are those, including myself, that do not agree with the anti-K&N BS that has been posted here. I have used K&N units on many different dirt bikes and off-road vehicles, and have never seen an incident where intake dirt caused any problems with cylinder wear. If the K&N unit is oiled properly, it will filter as well as anything out there. My current truck has had the K&N filter for 145K of the 165K on it. Its been used in a variety of very dusty environments and the last compression check I did (10K ago), was excellent.

1994 3.0L 4x4 pickup.
4.62 gears (4.22 stock), 33x10.5 BFG MTs. LSD rear. Five speed trans. 172K
Previously owned Mitsubishis:
1986 2.6L 4x4 Mighty Max, 1985 2.6L 4x4 D50
1987 2.6L Raider, 1989 3.0L Raider
1995 Montero SR