I have a K&N on my turboed Rhino. Never been a problem taking in dirt or dust until I rode on some roads in Co. this summer that was a very fine dust. It would cake up on the filter and when I cleaned it, there was some very fine dust inside the throat of the carb. I made an outer cover from foam on the outside of the K&N and oiled it like the K&N. Made a huge difference. On my prior Chevy diesel, I ran a K&N until I had an oil analysis done and it showed a high silicone content. Went back to the stock filters. Decided to try one on my '08 diesel and found out that it sucks all the oil off of the K&N and messes up the Mass Air Sensor and would go into limp mode. Would have to use a cleaner to get going again. Also went back to the stockers on it. On the other hand, I have run a K&N with an outer ware on my Raptor since '01 with no known problems. Just my 2 cents worth.