Passat Variant 2.5 TDI V6 LMM faulty?

Hello.
I have a Volkswagen Passat Variant 2.5 TDI V6, manufactured in 2000 (105,000 km), and I've been experiencing the following problem for a few weeks: Whenever I give it full throttle, the engine 'bogs' down. This means it feels like the engine briefly stalls and then restarts when I give it more gas. And this happens several times in a row. Additionally, it no longer pulls well at around 2000-2200 RPM, but only starts to accelerate after around 2600 RPM. When driving on the highway, I used to be able to reach almost 230-240 km/h in 6th gear. Now, I can barely manage 210 km/h according to the speedometer. And in 6th gear, there's very little power left. I need to use 5th gear on inclines. Otherwise, nothing! Because I now have to drive in a lower gear with higher RPMs, my fuel consumption has also increased accordingly. On shorter stretches of country roads where I could 'easily overtake' someone, I now have to think three times before attempting it. A diagnostic scan on a friend's laptop revealed nothing. The laptop only showed a maximum RPM of 4450 U/min, even though the tachometer itself was already in the red zone. The TÜV also said during the last inspection in May that the engine was not reaching its full power. Now I've heard that the LMM (lambda sensor) might be defective. Others told me that it could also be the fuel filter.
What kind of error am I getting in the system now? Could someone maybe help me?
So that I know which parts I need to buy and don't waste unnecessary money.

Best regards

Holger

[Translating...]

Lässt sich gnaz einfach überprüfen.
VAG-Com - Probefahrt - Messwertblöcke 3 Lesen --
LMM sollte dannn 850-900 mg/h liegen.

Turbo ist Messwertblöcke 11

ist aber alles ihr im forum schon beschrieben

[Translating...]der Wert muss bis 3000 Umin über 720 mg je liegen.
Ladedruck mit kontrollieren!