Did you pull your ECU to check inside? - per the video, that part is done because it's where the intake runs to - ie. under the cowl where the filter would be placed, it then runs straight toward the passenger side before turning into the cabin/fan area - it's kinda interesting they run the back of the ECU in that airstream for cooling
Speaking of the HVAC fan, did you already pull it to see how bad that part might be coated?

 

I haven't pulled the ECU because my air compressor is mounted in front of it and would be a major hassle pulling the air hoses and wiring out, and I'm in the process of adding ditch lights and doing PM (Preventative Mainteance) on the front suspension for the upcoming trip.




It's on my to-do list, on top of the aforementioned ditch light project and general maintenance. When I pulled the cowls, a couple plastic fasteners broke off due to age, and the weatherstriping started detaching from the cowls. <sigh> More parts to replace. They're really weatherbeaten to nasty gray so it's time they got tossed anyways...

 

i cant see the filter needed to be changed yearly… maybe every few years

 

OK, but annual replacement is what regular cabin air filters need replacing at.

 

ford also says to change the engine air-filter yearly, but im not sure that needed either.

 

Oh, yeah that's obviously usage based, and whilst it can be argued the cabin filter is as well, try looking at any cabin filter at the 12 month mark, they all need replacing if the vehicle is used at least a few days a week, this isn't Ford change interval, it's pretty much all the manufacturers - it's used all the time.

 

ford also says to change the engine air-filter yearly, but im not sure that needed either.

 

I've simply accepted that I will probably die 6 months earlier because of poor air in my truck.

 

You will, at exactly 6 months

It's honestly climate and condition dependant, live under trees? live in a more damp state? mould spores from the damp is all possible, live in a humid state, wet HVAC from clearing that out is a thing too.

Most of us don't have a problem.

 

Sarcasm or are you just putting out nonsense?

Yes, replacing any air filter like that more than once a year is not only recommended, but required. Just because it "doesn't look dirty" doesn't mean it's still good. Same thing goes for HVAC filters, home HEPA filters, water filters, and respirators. Please stop with the bad information on here.