Oh, I'm sorry I wasn't clear. I was assuming we weren't talking about a filter that requires you to cut it out and that's not changed at regular intervals.
As far as catching smaller particulate matter, I'm not sure I was clear there either. Over time as a filter catches dirt and dust it further closes the pores that allow air and anything else small enough to pass through. Check number two here:
http://www.cumminsfiltration.com/htm...g/faq/air.html
When dynoing one of our race cars(SCCA Spec Miata's.) we determined that the K&N filters are more restrictive than cheap paper filtration. The difference was substantial and it was even more so when dealing with a restrictor plate. Keep in mind that I'm not talking about custom K&N intakes, this is strictly with the stock airbox using different elements. We didn't test the cone intake filter as the 1.6l 1991 car can run any filter you'd like and the one that is on it is huge.
I have also run K&N in all of my vehicles, I would rather have a longer life filter than peak flow.
I apologize for being snarky, I had a bad morning yesterday, I should have asked a couple of questions rather than been an ass.