The 6.7L MAF is a very delicate sensor as mine has been replaced twice under warranty, turns out the real culprit was a stuck VGT. As for the K&N, I completely agree that it moves more air, but if you've ever seen the blades of a diesel turbo that has been running one for several thousand miles, it may change your mind. There is a fine line between too much oil that ruins the MAF and not enough that allows dust through. The grit that is allowed through wears off the edges of the turbo wheel. I still run them in my gas engines, but not in the diesels. The new Ford air intakes are made to flow enough air for up to 600hp without modification. I've changed every air intake on every truck I've ever owned, up until this one. Talk with some mechanics, look at true dyno data and look at the filter rates put out by the companies. Then go look at the independent testing facilities that have tested them. They are not all made equally that is for sure.
2016 Montana 3790RD Legacy Edition
Onan, TST TPMS, TrailAir pin, 8k Disc Brakes
2013 F350 DRW 4x4 CC LB
Viair 10007, Ride-Rites, Westin HDx, 12k Smittybilt