Rock-It Air Intake
Turbo City Rock-It Air Intake and K&N Filter
There are many discussions over the merits of the K&N filters on many discussion boards on the internet. Most argue, and I agree, that you need a prefilter to capture fine dust. This is especially true for those of us that live in the southwestern U.S. where its dry and dusty.
I found a review for Outerwears prefilter in one of the many trade rags that come across my desk. Its waterproof and does a good job on small particles. The review was quite positive, so I ordered one.