They don't filter nearly as well as paper filters. I don't mean slightly worse, I mean 40x as much dirty gets through. That's because the pores are much bigger to allow less restriction even with a smaller surface area (due to fewer pleats). Googling will turn up some experiments that show just how bad they are.
Either stick with a quality paper filter in the stock airbox or buy the Ford Racing CAI which uses a disposable filter. Sent from AutoGuide.com Free App