MAF readings from the cheap sensor
 

Attachment 83178 typical readings now, but at unknown speeds

My fuel trims stay pretty much similar, bank 1 to bank 2, with long terms rising as high as 8%, and the short terms trying to balance them out (negative 8, 9)= net zero or under +4% mostly. The problem seems to be is that mine rarely is driven, and when it is, on low speed short hops. It does much better on long hauls at high speed (which for me lately are 8-10 miles at 65-70 mph).

Take yours out for a true work-out, and find your fuel trims from that.

So my trip up and down the hill gave a ton of data. I feel like the short term for both banks was living in the +20 area while driving normally.

If lambda values are like Benz readings, a reading of 1 is perfect fuel mixture. +/- of fuel trims should be close to 0. My guess, there is a vacuum leak on the intake side. MAF readings should be close to engine size at idle.

I feel the same. I will do a smoke test tonight and pay attention to the intake side.

Smoke test yielded no results other than a trace amount of smoke coming from the disa valve. I rebuilt this a few months ago and checked the new gasket and the fit is very tight. Gasket is not binding so perhaps it's coming through the vein. But regardless, very small wisp of smoke, nothing big. Spent a solid hour smoking this engine out and nothing anywhere. Visually inspected everything notorious and found nothing.
But an odd thing happened: when I put it all back together and fired it up, ran very smoothly off a cold start. Totally forgot that I forgot to plug the MAF back in, and when I did, it ran worse than before! Short term trims were around 20! Another thing hing is that my "trans fail safe" light comes in when my maf is unplugged, I assume to protect the powertrain? Also learned that my maf is a cheap rebuild from Amazon.
Are all signs pointing to maf replacement now?

Yep I would say that is a good next step!

Both X5chemist and I are running a cheap MAF from Amazon, with great results. They are new units, not rebuilds, and have surpassed our expectations. I like mine so much, I used a refunded purchase amount to buy a second unit, for a spare. For $21, it is well worth the price. Try one, it might work for you, too.
Attachment 83181

I think he said that he found out his failing MAF is one like you and X5Chemist are running.

I mentioned that because I figured a part like that would be more reliable as an OEM part. This particular one was in the car when we bought it and we've had it now for two years and about 25,000km. I'm up for trying an aftermarket one, this car has been costing quite a.bit lately, and I may need a new and module.

FYI mine came from eBay. Same part number and manufacturer. Reviews show it can be a hit or miss. More positives is why I tried it out.