Technically speaking, if you opened up the exhaust and added a fuel controller at the same time, you would see marginal gains, but nothing worth spending the money on a K&N for. The factory filter in the wolverine is actually quite good, I would stick with that just for ease of use if nothing else. I have not researched the effectiveness of filtering in a K&N vs an ATV oiled foam filter, however for streetcars I am very familiar. K&N's do not filter as well as a stock paper filter in a car or truck, as the holes in the mesh are larger, so they let bigger particles through. But in the same token, they let more air through as well, which is where you see the HP gain. Still not worth it to me.
These guys have steered u in the correct direction. I never use a gauze type filter on an off-road machine. I learned this prolly 15 years ago when I ran one on my 400EX. When I would take it off for cleaning the intake boot would always have a super fine coat of dust. It was minimal but it was there. And I always properly oiled the filter. Every since then I use oiled foam style. The slight bit of airflow you gain isn't worth the increased wear the machine will get with the gauze.. I like a quality foam filter oil as well. I don't use engine oil. Klotz is what I've been using for over a decade.
Agreed. For something run through the mud, dirt, and dust, I won't use anything but an oiled foam filter. If I change filter from Stock, it's a UNI foam filter because they do make a good, dependable product.