I have a K&N filter on my 01 426 and it works great, I ride only in the dunes so I use a K&N prefilter, which restricts by 10%, but the filter is 30% better than the stock one, so I am 20% up. You do not oil the pre filter, so the sand and dirt do not stick to it like some other prefilters. The prefilter also helps deflect the water. No complaints here. Also, I was previously fouling plugs on occassion, the K&N has seemed to balance things out....haven't fouled since.