[Raine]

You have to bear in mind HOW more air is let thru. The stock air filter is paper, where as a K&N is a fabric. More precisely, the K&N is an oiled fabric wrapped in mesh. Although not as restrictive, the K&N has more "pockets" in it's surface by which to trap and hold particulate debris that may enter the intake, and the oil holds more dust than the paper repels. For that reason, the K&N may well prevent more pollutants from entering the engine while still improving on airflow capacity... but there is of course a higher level of maintenence required.