I will never run a K&N in my FJ40 or any vehicle that sees dusty conditions. After seeing how much fine dirt was downstream of the filter, I installed the paper element and the K&N has sat ever since. I wish I would have listened to my friends when they told me I was wasting my money.
Maybe they are ok for a street truck that never sees dust but I live in the country and gravel is a way of life sometime.