And, MAKE SURE to buy a Pro Design Pro Flow filter plate with your choice of UNI or K&N filter. That should positively be the first thing to buy period. You can pick them up on Ebay fairly inexpensive, or if you want, you can get them from RockyMountainATV.com.
The stock filter setup sucks, and if not anally looked over every single ride can leak and suck dirt in. Even with looking and taking care, it can still come loose while riding and suck dirt in, best thing to do is to just get rid of it and get a Pro Flow kit, you'll get more power to, but you'll probably need to go up on your main jets a couple sizes.