I spent the big bucks and got the K&N pod filter kit for my 550k. I use K&Ns in all my Jeeps, and there IS a difference. As for the "particulate matter", it's usually owing to one of three things: 1) not oiling the element, 2) OVER oiling the element (oil droplets are pulled off the media and deposited as "particulate" in the intake), or 3) Using pressurized air to dry them, which blows holes thru the media thru which dirty air can pass.
I've never had a problem with mine, and do notice a difference in performance. I've rejetted to compensate, and don't mind the little extra maintenance once every month or so.