I doubt very much that K&N designed the filters for the Apache, Abrams, Bradley etc. and their computers, with added horsepower over stock filters in mind. They are proprietary filters that are as big as they need to be to allow sufficient air flow, with an emphasis on filtering out MASSIVE amounts of crap from all sorts of climates. Obviously they did a good job, how much those filters resemble the filter in your Mustang remains to be seen. But I'm guessing there's a WHOLE LOT more to the filter in a 60 ton MBT than the ones you can buy at Autozone for 40 bucks :)
It should also be noted that all of those vehicles (especially the Helicopters) are PM'd, inspected and worked on daily, in some cases more. And will never be expected to drive the equivalent of 100,000 miles, or anywhere close to it in the case of tanks.