The K&N is a nice filter. But, you lose protection from water ingress. And, it can get muddied up when driving in the rain. I have one. It came with a bike that was modded for track-like looks. He removed the fenders, including the inner fender, on the rear, which allowed street irrigation run off to spit directly onto the filter from the rear tire.
This bike also had short bars on it and when you turned right, it stretched the clutch cable and it disengaged. He quite literally abandoned the bike. I got the bike through a lien sale. I restored most of it (including the stock air box) and it became a very nice bike to ride. I did sell it, eventually.
Cheers,
