Most reputable companies like Holz Racing, Pro Shop, SDR, Dasa & Muzzy sale / recommend using the gauze (K&N) style filter. Others like Hunterworks sale / recommend oiled foam style (UNI, Twin Filter, ect.). It seams like the general consensus from reading other posts in regards to this subject is the gauze style passes more air, but along with the air is dirt. Coming from a dirt bike background for the last 20 years, the foam style seamed to get the job done. Just curios why these companies seem to prefer the gauze style over foam. I am just trying to find the best filter for my money.
Now to make things more complicated UMP is in the filter game with a non-oiled Donaldson filter.

I had bad luck with a foam UNI in my RZR the stock paper was ok but now Im running an UMP and it works the best

I run a K&N but man that thing collects dust! I can feel the motor gasp for air. I am not a big fan of foam filters niether. I keep hearin good reviews on the UMP filters so I will be following this post!

I answered in more depth on the other forum, but I really like my UMP for desert use. Doesnt clog with dust or silt, and I can go a whole season without even looking at the filter, let alone cleaning it.

Theres others Forums? JK .............. Thats pretty good 2 ride the season without servicing the filter after every freakin ride!

what is a UMP filter

Check this site Gary Yamaha Rhino - Performance Upgrades
I usually google stuff when I dont know what somethang is.

http://ep.yimg.com/ca/I/yhst-4891263...5_2089_4027197

UMP Review on Off-Road.Com - - Off-Road.com

I know the UMP is well known in the offroad race community and they just came out with one for the teryx.

The Ump seems to work well but it does leave power on the table. By opening the end of the canister I picked up 2 tenths in 450' on a RZR.