Ford F450 V10- Long Term Power Loss Issue

Hi first time posting other than the welcome mat forum.
This is a service truck I use for my business. 2009 F450 V10 automatic trans. 645,000 miles but this engine has ~200,000 miles on it. Previous owner drove all highway with no towing ever and the truck was meticulously maintained. Its had a harder life with me for the past 30,000 miles. For about a year now ive been stumped on this issue. Its a power loss (gradual over time) that hasnt caused any misfires or poor drivability. Its been very consistent. All the multiple time Ive done a power contribution test over the past year, its given me pretty consistent results. Cylinder 2 is the least contributing. Cylinder 6 and 8 contribute more but are showing an issue during the test. Though just now as of reviewing my most recent video, it seems 1 is dropping out in place of 6 during the highest load during the test. Under load pulling a hill with an empty trailer has given me the best examples.

Other testing Ive done is:
Swapping coils with known good cylinders
Swapping injectors with known good cylinders
All plugs have been replaced and then later on swapped with known good cylinders
Power contribution test always came back with same results.

Finally did a static compression and running compression test on a handful of cylinders after making a 12mm adapter that could reach the threads down in the heads. All tests came back very close. 
Static compression
#1 185psi
#2 185psi
#3 185psi
#6 185psi
#8 190psi

Ive included a video of how I did the running compression test. I spent alot of time messing with the length of my compression tester hose and skewing results but in the end I shortened the hose as much as possible and believe that all the cylinders are providing very close results. I did not record results because of this other than a handful of videos i saved. Of the cylinders above, they all showed 60-70psi while idling. Then after snapping the throttle 5-6 times got to 170-180psi. Of the various info Ive got on doing a running compression test, my results Im not for sure are correct but the similarity between all cylinders makes me believe I dont have a mechanical issue specific to any cylinder.

Fuel pressure is good at idle and snapping the throttle. Does not seem like fuel pressure loss under load but I cant recall now if I tested that months ago. Cat converter has been gutted. Manifold air pressure tested with a vacuum gauge. 20inches at idle, drops and goes up to 22inches when snapping throttle. MAF cleaned. O2 sensors replaced with name brand. Ive checked O2 signals and fuel trims while idling but wasn't sure what to look for while driving. Valve cover removed and valvetrain inspected on drivers side bank where I have a lifter tick on warmup. Engine (Ford Reman) has updated roller followers to prevent camshaft failure that these 3V engines are known for. Spark plugs look lean to me but I could be wrong. Any advice is appreciated.

Thanks!

I was planning to upload a video of the power contribution test, the relative compression test and  2 photos of spark plugs but am having trouble with that. I'll be trying to figure that out if it doesn't all show in this first post. Here are some links at least to them uploaded to photobucket.

Power contribution test
photobucket.com/share/bbfabcd9-8483-4058-a903-e35aad287679

Running compression test
photobucket.com/share/1d6f594f-7e7a-4b0e-a714-fb470fdf05a0

Spark plugs
photobucket.com/share/4288c457-7faf-4be1-b144-143d0a30240d
photobucket.com/share/d435bdf6-88e1-49a1-9dbb-46edc3880f5d

Ford V10, don't see too many of those. I've never seen a 3v version! So that means this is a VVT engine?
So, when you say gradual power loss, this just generally feels like it doesn't make as much power as it used to or it starts out feeling normal and gradually loses power over time drive it?
How much of a loss of power are talking here? Is it cutting up and stalling, not making it up steep grades, or just kind of enough to make you think it should be better?
For what it's worth, I think your running compression test results are fine. I expect half of cranking compression at idle in most cases.
The relative compression you shared won't load for me.
The cylinder contribution test on the scan tool, from what I remember is to help find a single low contributing cylinder at idle. As far I know, all bets are off when driving the car or raising the rpm, but I could be mistaken. I just don't use that test off idle or with more than one cylinder misfiring. Considering you dont have a misfire, that test probably isn't going to help much anyway.
I see you cleaned the MAF. That's obviously not fool proof, I would check calculated load at wide open throttle, shirt and long term fuel trims on both banks at idle and across all operating conditions along with MAF grams per second and if this is a 3v VVT engine I would watch the VVT loop status and error pids.

Yes they made the 3v versions from 05 and actually continued them in the medium duty trucks up until 2019 before they came out with the 7.3 gas engine. They do not have vvt like the 5.4s though.

The power loss progressively got worse over months but it was subtle and gradual. When driving it is very consistent, no changes except, Ive noticed many times while towing on a longer trip, that after about 15-30mins of heavy towing, the power actually starts to come back and it has the low end torque again to hold taller gears.

Most people wouldnt know anything is wrong with it by the way it runs. No stalling, no misfiring. Would always make it up a grade just not like it used to. Coincidently yesterday I had a grade which I could not make it up. A very steep short hill I had no running start at, I had to shift into 4x4 low to make it up with heavy trailer load.

Good to know on the running compression test. I mis captioned that video. That is a video of the running compression test. I fixed the caption now. The video loaded for me just now. Did the power balance video load? I was wondering if the power balance test could be leading me in the wrong direction like you mention it not for running tests.

Yes I would like to take a look at the MAF readings while driving. Yesterday I watched some scan data while driving and fuel trims seem perfect. O2s are switching the whole time. MAF numbers would go up but data is in lb/second so I wasn't sure what values to expect. I'll look into that more now. Knock sensor values were going up with load and with rpm under engine braking. Im not sure what Im looking at there either I'll have to get educated on those.

Another thing I've been thinking about is this engine has some sort of intake runner adjusting servo. I dont know anything about it besides Ive seen these things on other engines. Scan data said the component ("intake tuning valve" I think it calls it) is operating and it is switching on and off under high rpm loads above like 4000rpm.

I will also note in that range above 4000rpm and sometimes below when it creates this symptom more, I intermitently get a high pitched ringing/whistling sound. May be an intake related problem Im starting to think.

Thanks