Well guys hate to burst your bubbles either way, but the latest trailer life with its renown motor editor has just included an article on "how to gain power" and it has them installing new cold air filter kits. Although not specifically K&N they do have some others.
A lot has been made about oiling and cleaning and the K&N does become more effective if left a little dirty looking. I clean mine about 1 a year and it usually looks pretty grungy. OBTW, the truck has over 300000 miles with about 210000 running the K&N! Matter of fact it was recommended by a major exhaust manufacturer to add a K&N to my old f250 gasser along with a free flow exhaust system to aid in towing my TT.