I bought a K&N drop in, just because it's only twice the price of a stock unit, and it lasts a lot longer. In the long run, you save money. Anything that lets more air in by nature won't filter quite as well. Something has to give. However, I maintain my car to a high mechanical standard and don't believe particulate ingestion to be a major concern for me. I notice no gain in performance, throttle response or gas mileage. If you were going to buy for those reasons...don't.