Need Advice on E450 Engine Mod

I have well above 200k km on my k&n filters with no engine problems I have driven all the cars I've ever put one in to 300k km before a non engine related part or system went. I will admit my work partner drives an f150 with a k&n oem replacement I got to see it one day and will give ford cudos on their attention to respiration of their engines they seem to put really big stock filters and air boxes in them. With that in mind I might avoid the CAI and instead use that money on a tuner or exhaust or better yet a suspension upgrade if you have a little more control over sway and bucking you should see a mileage improvement.