Golf 1Z: No Power? Troubleshooting Guide

Hello fellow TDI enthusiasts!
I bought a used Volkswagen Golf 3 TDI about two months ago. It's from February 1994, has 90 horsepower, and the engine code is 1Z.
bought
At the beginning, when I transported the car from Wiesbaden to Stuttgart...
He was driving at a perfectly normal speed of approximately 190-200 km/h on the highway.
It pulled well from the bottom and everything is okay.
After about two weeks, the car's maximum speed was limited to between 140 and 160 km/h.
After reading in the forum that the mass airflow sensor (MAF) might be defective, I replaced it, along with the boost pressure control valve and the turbocharger pressure sensor. This was because when using a diagnostic tool on my VW, intermittent 'intake manifold pressure regulation difference' errors were being detected.
Okay, so I installed a new turbo. It definitely has more power now; the car accelerates better and runs smoother, I think. However, it still goes into limp mode between 140 and 160 km/h.
If you quickly release the accelerator and then immediately press it again, the car will sometimes reach speeds of up to 180 km/h.
I'm really at a loss.
After I've replaced and checked everything, I don't know what to do next.
I have the LLK; I extorted it from him. Everything is fine; there's no loss of pressure.
The turbo delivers full power at 0.9 bar.
except for the one that automatically adjusts back to 0.6 bar when it reaches 140 (emergency mode)?
I am grateful for any help.
Best regards to Chris from Stuttgart.

Take a look at the technical articles and specifically the section on troubleshooting TDI engines using VAG-COM. Without proper diagnostic logs, troubleshooting is like groping around in the dark.

You should have invested your money directly in a VAG-COM interface instead of first trying a new (expensive) charger, which ultimately wasn't the cause of your problems.

EDIT: Have you ever considered just trying it out by throwing away that 10-cent piece?

Regards,
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It can also be used as a verb, meaning "to gust."

hello guste
Okay, it's not the 10 cents because that only increases the injection amount.
and has nothing to do with boost pressure.
Furthermore, whether using 10 cents of fuel or not, it performs the same at 140 km/h.
Already between 100 and 110 km/h today.
Best regards, Chris.
I now think it might be the control unit.