I agree Mark, plus, you can get a precharger to go with them if you like to filter extra dust out.
09KLXowner. I wouldn't use the RC and MC point you made as rock hard evidence. Those guys run whoever pays them. They have their motors rebuilt every race and they are riding on watered down closed course circuits, putting no more than a hour or two on their motors before a rebuilt. You could almost get away with just clamping a piece of an old T-shirt over the intake at those rates.
K&N's do alright, plus like I said. Theres prechargers too to prefilter dirt before it gets there. Plus take into effect, you only need that super high filtration if your doing alot of dusty dirt riding. We use dual sports so some if not all our riding is on the road. Street bikes usually have just single layer paper filters like whats in a car.
So really it all depends on what your doing. I personally feel if your using this bike for dirt riding under REALLY dusting conditions I say toss the twin air and UNI out the window and keep buying the stocker. Have you guys seen this thing? its like an inch thick of super dense heavy foam. Nothings getting through that. The UNI's and Twin Air's pass more air as well. Espeically the UNI, that course outer layer definately does before it hits the finer foam. Yes the finer foam does a better job but its not as good as having an entire filter made form it. So I wouldn't depend on UNIs and TA's as the filter of God or anything. Like I said, all depends on what your doing. I almost bought a K&N myself and probably should have because they are garaunteed for a million miles but the price put me off, so I went with a UNI.