Yet another "no power @ high RPM" 02' 5sp wagon

Hey guys. this is my second TDI, i had an 04 5-speed BEW a few years back. Great car.

Last week i picked up an 02 5 speed wagon. 200k miles, its had a lot of maintenance done (although apparently not to the engine), and what appears to be a new injection pump.

It's got two issues that the ALH has become (in)famous for:
1: rough idle (i'm fairly certain it needs a DMF but, the injectors don't sound consistent either. one seems to "clack" a lot more than others at idle)
2. This is the most concerning to me... a loss of power at high RPM.

For the latter: it gets worse with each higher gear. In first , I get to ~4Krpm before it falls on it's face. 2nd: ~3500. 3rd: 3k. 4th: 2700. 5th: it puts out just enough oomph to get the turbo spooled before it fizzles out.

cruising along at~80 last night, in and out of full boost (lots of hills here in CO), I received the dreaded p1248 (first code i've seen). when i lose power, there's no smoke in the rearview. even when the car is in boost, there's no visible smoke. Additionally, maybe its just old vs new tech but, the BEW seemed much better in every way: Spool/lag, power under the curve, midrange, you name it, my ALH is a dog in comparison.

Here's what i've done today, to no avail:
1. adjusted fuel timing, this was off the charts (advanced) in VAG-COM. Dead nuts now. midrange seems better, still crap idle and top end though
2. hammermod. i'm at 4.0 now, was at 3.5 before. Played with some different values but... no difference, with either issue.
3. replaced Fuel filter.
4. ran an entire can of diesel purge.
5. cleaned the MAF (which was filthy but, did not fix the issue)
6. ran with the maf disconnected. Spool was awful (build boost more like a supercharger with a max of ~12psi) and overall, the car was extremely sluggish.
7. checked mechanical timing, looks okay. the pump lock hole and flywheel marks like up (can't tell on the cam, dont have a locking tool)
8. checked cam lobe wear. not "new" but, nowhere near enough wear to cause an issue.

Here's a video of the rough idle. the "clack" seems to get worse after a drive.
https://photos.app.goo.gl/p475NTaHWy5HmHno7
Here's a link to the raw logs
https://drive.google.com/open?id=1FsJyugFYE2qrH6M4buphbsxoJ3VElv_O

I appreciate any insight you guys can give me!

I'm sure more folks will chime in, but the first thing I'd do is check or clean or replace the N75 valve. The vacuum tube that comes up from the turbo actuator plugs right into it. In your 3rd pic down, it's the black and white (on top) little unit by the firewall. To its left is the check valve. Both of those would be worth a look.

Check the EGR valve/intake manifold for soot clogging.

Sounds like one problem could be fuel starvation!

You can check the fuel pick up in the tank as they can get plugged or restricted with crud and build up.

Maybe the car doesn't like Michelob. Try a some Bud!

It feels like fuel starvation. It's not necessarily tied to a particular RPM. It'll run WOT for a few seconds, then loose power.

What I tried today...
1. Swapped the n75 for the egr valve actuator, checked for vac leaks, and lcleaned the check valve... No improvement.
2. Pulled the fuel pickup assembly out of the tank. It was pretty clean but, I cleaned it anyway. I also drilled out the check valve that some have deemed problematic... No improvement.
3. Checked for intake clogging, nothing too bad. I'm 99% sure that's not my issue though. It'll run hard at higher RPM... But just for a second or two.

Update for anyone who has a similar issue...

It was a bad MAF. I pulled the maf sensor from my Mercedes OM606 (swap project) and dropped it in. Wuzzah: faster spool, consistent mid-range, and that elusive top end. Pulls hard (for a tdi anyway) in all gears.

The correct MAF replacement is in the mail but, for now, this will do the trick.

That p1248 error code must have been from the overly advanced timing.