UPDATE:
The truck has been running great, no Mil light.
Data log from last wed with the new Maf sensor.
https://drive.google.com/file/d/12HHfxZqBgnBm-A1zdWrmOHUCM-p15tYJ/view?usp=sharing

I installed the old sensor for a few days as requested and the LFTs seemed to become somewhat inconsistent, Friday they were high around 10, Sunday they were only slightly above normal and today they went up to 11-13 during cruise. Interestingly they never got as high as they were before the sensor was replaced. Which could be just not enough mileage yet. It does not seem to have proper throttle response with the old sensor. It feels slightly lame at times usually when passing cars. It feels like it takes more throttle to make things happen. But that could also just be in my head.
I do have some data logs if you want to see them. I will be reinstalling the new sensor tonight.

One more dumb question.
Short of actually drilling a hole in my exhaust, what should keep an eye on to see if the small exhaust leaks (in previous pics) are actually starting to cause trouble? ( Im assuming Lfts and equivalence ratios)
I plan on repairing them but would like to wait until winter when Im not driving the truck.

Ha ha refitting the old Maf... That's Brilliant! (not sarcasm) I glad I havent binned it yet. I will give it about a month and try that.
How long would you expect it to take the fuel trims to go crazy again?
It took the rush hour drive thru town and a few miles of cruise to see the results after replacing it. (Long enough for me to think I had just spent $450 for nothing)
The real test will come in fall when it gets colder and the air gets denser. But we may still get some cold spells yet. I did have the Mil pop up over the weekend before I got the new Maf.
I wish I had actually calculated my fuel mileage before changing the Maf, to see if it actually changed. Im not sure how the readout actually calculates it and how accurate they are, time will tell I guess.
I am a little disappointed though, I drove an hour+ one way, paid Land Rover dollars and was then handed a Denso Maf sensor. Which I could have purchased locally for half
the cost.
Oh well c'est la vie

Sorry for the slow update.
I got the new Maf sensor Tuesday night. So i did some logging in town before changing it
Before
(https://drive.google.com/file/d/1P7uLioEd1aluSqYxnfKfkvewuUksglFg/view?usp=sharing)
After
(https://drive.google.com/file/d/1F0-n0PV_FdNlk4sUieRhfmnTVwLolh-e/view?usp=sharing)
It took some time but the fuel trims did eventually come way down and I think the fuel pressure increased by a few pounds as well.
This one is after about an hour on the drive home using same road I have been doing most of my data logging on.
(https://drive.google.com/file/d/1EPTpIeFx7HYfgQrzf0WXKXcF4qtsEH0Z/view?usp=sharing)
So far I like what I am seeing, I will probably pull some plugs on the weekend to confirm this.

Maf sensor should be here tues or wed of next week

Ill see what happens. might take a few days though Its cold and crappy here still for the next few days.
Im thinking I should change the Maf anyway since it is most likely polluted with oil from the previous air filter. I need to get some exhaust gaskets anyway

Some would call that cheating. LOL (instead of trying to find everything the electrical drawing) I assume you have to cut them all regardless. Easier, faster, why not?
I dont mind buying parts once im sure they are the right ones. And this is now starting to make sense.
Ok will do
I assume you want me to log data as per your list earlier?

And I assume this should be done with engine at operating temp,

Should i do this before or after changing the Maf?

You are not cutting me off. We have eliminated every thing other than some possible very tiny vacuum leak.
I will try unplugging the injectors which in simple terms sounds like it will cause the ecu to relearn parameters based on the actual wear and tear of the engine. Effectively relearning the base fuel trims for the current condition of the engine.
As per my previous post I think I understand where we are on the trouble shooting and the Maf sensor makes sense. Also since the holes in the exhaust are downstream of the upstream sensor. I dont think they would really affect the upstream sensor readings, Which I think you mentioned are the primary drivers of the fuel trims.
Other than a decent Fluke multimeter I have no other tools available to actually check each sensor out. And without a base line it wont mean much. Im learning stuff here so Im happy. Let me know if Im getting it correct.
What? I have fuel trims for all 4 O2 sensors? How did I not see that! Getting old sucks.

Holes in the exhaust would cause the O2 sensors to report a lean condition, thus directing the ecu to add fuel. If the right amount of fuel is being added, that would show up on the spark plugs as a rich condition provided no extra air is being drawn in. But if the Maf is under reporting the amount of air. It lowers the the amount of fuel added and also lowers the actual amount of the fuel the long term trims have available. Which then creates the high readings. Because the reality is not enough fuel is being added since the sensor is under reporting. And this would then actually show up on the plugs as a lean condition similar to a vacuum leak. The Ecu then uses this along with barometric pressure, air temp, engine temp to then determine how much fuel to add and also how much fuel pressure it needs.
If I got this correct, it has not been a worthless exercise. I have actually learned the basics of the system system operates.

Davew
You do have it right. They are short pcs of pipe but the humidity and salt they use on roads here makes exhaust work difficult. Any weak parts are usually broken as soon as removal is attempted which can snowball into a lot more work. As you can see from the pics access is difficult. I didnt mean to offend, I just needed some clarification on terminology.
Environmental conditions here are different to yours. We have constant humidity except in winter and then they use salt on the roads. Because of this ally and steel here, do not play well together unless very well isolated. Any hole in the exhaust system will continue to grow at an increased rate. This area of Canada is known as the rust belt. Most vehicles wont make it past 15 years. This is not something anyone would know unless you have spent time here.

Fair enough. I like to determine and validate things first. we have eliminated almost all of other possible causes. I was coming to that conclusion as well when I seen the date on it. And when I repair the exhaust I may have to replace the O2 sensors anyway if they dont survive. At least Im not throwing parts at because Im just guessing.

Has my exhaust been changed to the 5.0L? On the JLR site it does not show that for the 4.2L exhaust

So the exhaust for the 4.2L and the 5.0L are the same? I could probably find some decent used ones here if they are the same. The older 4.2L are getting scarce around here but 5.0L are easier to find.

So why the Maf? Due to age? Or simply to hard to determine if it is reading out of spec. (sort of a preventative measure).

I think by jubilee clip you are referring to what we would call a hose/screw/gear clamp. But I have no idea what "ally" is.

Easily? LOL They put these things together like an F1 car, except the forgot that it only takes 2 people about 5 min to remove the body to gain access. No special tools required.
I did notice that. Are these pipes available separately in the UK? I looked on lr parts direct and they are not shown separately. It appears they come with the manifold or the catalytic converter. Neither of which is anywhere close to an economical repair here. Matter of fact the cost of replacing the cats at dealer price exceeds what I originally paid for the truck.
I do have the ability to make new ones myself but getting the alignment right is particularly difficult due to warpage while welding. So I would prefer to just replace them.

Yea, we have something similar. Most dont stick for more than a few months if not prepared properly. Biggest problem is that i can barely get my little hand in there let alone a tool. Wire wheel, grinder no chance of getting it in there. I will see what can do today. It will only be temporary but good enough to prove the issue.
I also have the option of putting more weld on it. Might get me thru to winter when I wont be driving it anyway.
Same as the previous person with lots of hope and good intentions. LOL
Unless I can figure out how to see thru my tools and body parts LOL

I did do a visual for exhaust leaks when I first got the truck. And they dont make enough noise to hear. When I saw the welds I did remember them. But the telltales are not visible except in the pics. Even the holes are not visible in the pics only the telltales. Getting the phone in there for you guys meant I got angles and detail that no one would never see. Im not sure the stick with tissue would show these. Looking at the fueling traces the trims only show and issue once the revs are up with engine load after is settles into cruise. There may not be enough leakage to show up at idle.
I hadnt thought of the silicone. Might work for a few days to test. Ultimately they will have to be removed for me to repair them properly. There is no way to get anything in there to work with. I can think of 2 reasons that someone has done this.
1 They blew holes the pipe with a torch while trying to heat the sensor bungs.
2 Blowing holes using the welder instead to try to locally heat the bungs
Either way It was an on the truck repair where the welder is blindly stuck in there with the hopes of hitting the right spot and not burning thru. Since you cant see anything around the welder Then you just keep building until the hole goes away, Since you cant see where you are welding you have no control of where and how much you are putting on. Works for a while but blows out a few years later.
Im guilty of this myself, but a pinhole made no difference years ago. I have some pin holes in my winter truck with dual wide band sensors and it doesnt care, I didnt even set a mil when the downstream sensor fell out.