AFN Boost Pressure: Normal or Faulty?

Hello community,

I recently investigated the turbo boost on my 1996 Passat with the AFN engine and would like to ask for your expert opinions.

First, let's start with the vehicle data:

Volkswagen Passat GT Variant 35i B4; manufactured in March 1996; equipped with an AFN engine.
- 208,000 km
- Everything is stock except for the EGR valve which has been disabled, and the air intake snorkel by the air filter is missing.

Okay, I've now connected a measuring instrument with a range of -1 bar to +3 bar in parallel with the boost pressure output to the control unit.

Idling: 0.1 bar.
Full throttle in first gear up to 4000 RPM: Boosts up to 2 bar.
Gear 2, 1500-4000 RPM: It then regulates itself to approximately 0.9-1 bar from a maximum of 1.5 bar.
For all subsequent gears, maintain a maximum pressure of 0.9-1 bar under full load.

Under full power or with little to no gas applied, the pressure is between 0.1 and 0.4 bar, depending on the gas setting.

Why is this happening: Since I hardly ever drive on the highway (it's about time ), the VTG might occasionally get stuck, which then, when accelerating quickly from first to second gear, often results in a loss of boost pressure...
(I was able to reproduce the error once; in this case, there was clearly a lack of boost pressure after shifting and immediately accelerating.)

I've now replaced some vacuum hoses that looked like they were about to fail... and I thoroughly cleaned the VTG (variable turbine geometry).

'An LMM is also okay, as the test with the 1N4148 diode hardly showed any noticeable improvement.'

Are the values up to 2 bar in the first gear okay, or is there a problem here already?
What is foreseeable?

Okay, unfortunately, I don't have a VAG-COM either...

Best regards, Roland.