I too have an 08 F-150 5.4L
K & N been around a while but the technology today is far supreme, who needsoil for filter......not I ...I only spent $150 for my intake and "jjg" is not far off the price, I was told that CAI units are over rated and you could pull almost the same numbers HP & Torque by doing simple things. 1. Replaceing the stock intake arm (tube) with an unrestricted flow through intake tube polyurethane the one I bought was the Airaid M.I.T. $109.95 and 2. Replacing the stock paper air filter with a Dry Flow direct fit high performance air filter that goes in the stock air box housing, the one I got was AEM performance panel filter $39.95 no oil needed and the filtration and flow is tops, also one never has to worry about over oiling the filter, washable and let dry put back-in, stops 1 micron dust particles where K&N and other filters that need oil only stop 5 micron sized, plus I got dyno numbers close to you CAI units, I pulled 15hp/33ft.lbs. torque with $150 not bad, and Iam happy with that. The guy at the shop told me that these CAI units are for looks and the nice "whistle " noise they make some people like'em for sound but HP #'s they aint all that, saved my A$$ some money and used it to get and Super 44 muffler cat-system, figure if the truck is now breathing better then it better be able to exhale better as well, oh and the Super 44 is aggressive sounding muffler with Deep tone through all RPM's. This is just what I did and it worked for me and my budget, yours may differ, to each his own, I love these F-150's though, fun to drive.