You're going to get quite a few mixed opinions on this one...I for one enjoy the performance gains of a K&N Air Filter BUT I (personally) don't believe they are the best suited air filter for off-road purposes (ie. extremely dusty conditions). K&N Air Filters are made up of a cotton-gauze material and when compared to an OEM paper air filter, it's really easy to understand how the K&N can increase performance; they simply allow more air to enter the motor. However, over years of researching and conducting tests I've come to believe that this isn't necessarily a good thing in all cases. In order for the K&N Filter to allow more air into the motor, the filtration element has to be less restrictive than the one it's replacing. Obviously, cotton-gauze is going to allow more air to pass threw it than a solid piece of paper but this isn't a perfect world, so you must take into consideration that you're not only letting more air in, you're also letting more debris pass by the filter element. This is ultimately why we oil our K&N Air Filters. The oil helps to trap larger deposits and debris within the filter material in order to keep it from entering the motor. BUT the oil can not stop all debris SO, eye's point back to the filtration element...the cotton-gauze. By utilizing a slightly more restrictive material for filtering the air that enters your motor you can better safeguard it against these smaller deposits. It's this reason why I prefer to use a 2-Stage Foam Filter (Uni or TwinAir). I have been using these style air filters for off-road use for years and I can safely say that the performance difference between foam and cotton-gauze is very minimal AND I feel more confident that my air filter is safe guarding my engine from harmful dirt and debris.
