UMP is prolly the best to keep ALL types of sediment out of the motor, especially the silty real fine stuff. If you run in sand or heavier dirt the K&N system is the easiest to install and produces the most HP from my personal experience.

 

UMP

 

Whats the cost for the UMP? Saw it on ebay for $319. What type of modifications would be needed?

 

319 sounds pretty good. Need to remove the bed to get to the air chamber...once you have that out you need to drill a single hole in the chamber and you need modify the airbox hole to make it larger. Thats about the toughest part. For the average guy I would estimate about 2 hours labor to install.