I read somewhere that K&N filters rely on oil to absorb dirt particles and are not as effective as paper filters to catch smallest particles, like dust. This gets worse as the oil dries out and small oil drops being sucked with air inside engine could also damage MAP sensor. I used K&N filter in my older car without any problems, but I decided not use it in my TCH. In good air conditions you could probably run the car without any air filter, but in the area where dust is very common it could cause increased wear in the engine.