Famous K&N performance air filters are well known in high-performance circles for free flow, long life, and added horsepower. These high quality MK7 air filters straighten the airflow to give a better inlet feed than no air filter at all! Flow bench testing shows a 35% increase in airflow over the stock paper filter. The pleated cotton grid suspends dirt on the outside of the filter and will not cause significant airflow restriction for up to 50,000 miles of driving. Periodic cleaning and re-oiling restores the filter to like new condition. Autotech highly recommends the K&N filter as the first stage of performance engine tuning. K&N filters are emissions legal and carry a million mile warranty. All filters come pre-oiled, ready to install.