I run Uni-filters and I think they are better over K&N, but I have never run K&N. My thinking is that K&N say there is more airflow - but to acheive that the foam has to be more open, therefore letting more fine particles through.
the Uni-filter are foam and do require cleaning and oiling but if you have two or three then the job is not so bad, wait till they all need doing and youare set up to do them all at the same time.
Also, I got the snorkle pre-filter that I beleive is a good thing too (so much so I am thinking of contacting them for a pre-filter for my LR Discovery)
with the foam filters you can have them all clean and pre-oiled and then put them in a bag and then half way to Mongolia change it, change it in Mongolia and change it half way back, they pack up smaller than a original equipment paper filter, are quite cheap in the grand scheme of things and as they are all new and pre-oiled you dont have to take any cleaning solvents or stuff with you.
Unifitler recomend the use of Bel-ray filter oil
you will need to take disposalbe rubber gloves with you though, the oil on them is sticky as and a PITA to clean off youhands - especially if you are in teh bush!
avoid anything that says you can clean the filter oil with water, get water in your airbox, it cleans your filter and then you have no filter!
Hay Ewe