I've read many post stating K&N filters are not that great for us Jeepers, they let in way too much dust particles. Just my 2c
I have run a K&N in everything I own, my Jeep, Jess's Liberty, my Harley Truck, my Harley and my Honda Hawk, and in all of my previose vehciles, and in 12+ years I have never had a problem. They key is applying the oil after cleaning them. Too little and the dirt doesn't stick to it, too much and it gets sucked into the engine. K&N does more research and develpoment then any other air filter company. I would run a pre-fliter if I was doing Baja, but in this area it's not really needed.
When I was in college I took a semester of Automotive Engine Engineering and for a lab we tested a K&N, paper, and a foam syle filter. We tested them for air flow/ filtration/ and Dyno testing on a LS1. The K&N won at all three and made 10 HP over the paper on the LS1. The paper filter was next best in filtration, but third in air flow and HP. The Foam was worst in filtration, second in air flow and HP.