Stunning performance drops at 1Z

Hello Experts, who have had to deal with this topic frequently. After the enjoyable registration process, I now hope to receive more competent help here than in other forums. I have also worked through all the posts on the topic of 'performance decline,' but I don't believe that any of the known cases can be directly applied to my problem.
Current Status: I own a Passat 35i Variant with a 1Z engine and approximately 185,000 km on the odometer. The car has not been 'chipped,' and it is regularly maintained (including new filters, etc.), and it is often driven on long journeys, including frequent full-throttle driving. However, recently, I am trying to avoid long highway trips because the car is starting to bother me. Due to work-related stress, I tend to postpone problem-solving, but unfortunately, I've been doing so for quite some time.
Initially, the problem only occurred sporadically, but now I've been dealing with it constantly for about 3 months: a significant performance drop around 3000 U/min in 4th and 5th gear, i.e., under full load. The engine doesn't enter a permanent limp mode. After releasing the gas and pressing the accelerator again, the car accelerates for a few seconds before the problem repeats. There is no extreme jerking. Slight 'clouding' when accelerating in the headlights of following cars in the dark is - I think - normal - or not? So, to the garage.

Error log messages:
528 F96 Height Sensor - Open/Short to Ground
575 Suction Pipe Pressure Control - Sporadic Error
519 G71 Sender for Suction Tube Pressure Intermittent Short Circuit to Positive

All errors have been read out and deleted from the professional workshop. Statement of the master: Sporadic errors are not explainable, and the altitude sensor is unlikely to be responsible for the behavior. Advice: Keep observing!

Weeks later, re-reading: I wasn't involved, the master reports: It was just a faulty altitude sensor in the memory. Suggested solution: There must be a problem with the control unit, it needs to be replaced!

Workshop changed: Statement: 'Please leave the car here for 2-3 days, and we will definitely find the problem.' Last week, someone else had a similar problem here. The problem was gone after the turbocharger was replaced.

After extensive online research, I took the initiative:
1. LMM renewal - unsuccessful.
2. All tax hoses (red, black, and blue) checked with pressure pump - everything is OK
3. Hose to the control unit looked bad, replaced as a precaution - without success.
4. Control rod checked for functionality on the turbo, and pressure gauge checked - Working! I, however, no longer remember at what pressure the cable made its way.
5. Turboregulation valve passage (blowing) and checked for audible switching - appears to be OK.

In a last-ditch effort, I purchased a Vagcom and an interface connector and, after some initial setup, conducted a test drive, although I did so alone, which presented some of the expected challenges. Had to log a long distance and then painstakingly search for the relevant parts when evaluating.
Result: At a barometric pressure of 1024 mbar, the 'actual MAP' increases from between 2700 and 3100 u/min to up to 2083.2 mbar and remains constant until the power failure. Then it remains at just over 2000 mbar. After the 'gas pedal-kick' procedure, the pressure rises sharply again to the specified, too high value after a short drop. I interpret it as: The control unit tolerates the excessive pressure for about 2.5 - 3.5 seconds and then reduces the injection volume so that the pressure returns to a 'still acceptable range'.
The whole thing then repeats constantly. Interestingly, with a correspondingly large number of 'cycles', I can still reach 170 km/h. However, during the log, I also noticed that the 'Duty Cycle Boost Valve' value (freely translated: throttle position boost valve - correct? Group 11, 4th value?) is constantly above 90% and even reaches a stable maximum value of 94.1%. I once read and noted that this should only be 40-70% at full load. What exactly is this value actually? Which measuring values or sensors are used for the calculation? Is it an open or closed percentage, and what does the percentage refer to? Maybe this will help me find the solution.
Was a long lecture, but it's also a long story. I hope I haven't forgotten anything important. Thank you in advance for your help.

Addition: Also, I also checked the accelerator pedal potentiometer. Runs smoothly from 0 - 100%.
And: The professional will surely understand that I only have a simple (apparently) wastegate turbocharger, in which the impeller adjustment cannot be fixed.
Therefore, I am currently really at a loss.

Sven 01 wrote:

At a barometric pressure of 1024 mbar, the "actual MAP" increases from between 2700 and 3100 u/min to a maximum of 2083.2 mbar and remains constant until the power fails. Then it remains at just over 2000 mbar. After the "gas pedal-kick" procedure, the pressure rises rapidly again to the specified, too high value after a short drop. I interpret it as: The control unit tolerates the excessive pressure for about 2.5 - 3.5 seconds and then reduces the injection volume so that the pressure returns to a "still acceptable range".

Okay.

Quote:

However, the log also revealed that the "Duty Cycle Boost Valve" value (freely translated: Boost Valve - correct? Group 11, 4th value?) was constantly above 90% and even reached a stable maximum value of 94.1%. I once read and noted that this value should only be between 40-70% at full load. What exactly is this value actually? Which measurement values or sensors are used for the calculation? Is it an opening or closing percentage, and what does "percentage" refer to?

Control of the boost pressure regulating valve.
94.1% will be the "minimal pressure" setting. So, the loading pressure does not respond to the full regulatory intervention.

At 1Z, this valve (N75?) often causes problems... -> Search function.

Hi Ulf, if I understand you correctly, do you mean that this turbo-pressure control valve on the spray wall above the brake booster is the cause of all the problems? - Sorry - complete lack of understanding. And that even though I had checked for continuity and functionality! Can the valve do more than switch on and off? If I disconnect the connector, shouldn't the turbo pressure drop to 0.6 bar? - Or? If I still measure higher pressure, then it's probably not the valve - right? If that's the case, I'll try this tomorrow and, if necessary, buy a new valve immediately. I have still been delaying this due to the confusing findings.

Sven 01 wrote:

Hi Ulf, if I understand you correctly, do you mean that this turbo pressure - control valve located on the spray wall above the brake booster is the cause of all the problems?

Already possible.

Please find the technical article on TDI pneumatic systems (if not already done). . .

Hi Ulf, I just read the article earlier, but I'm still new to this forum and need to get my bearings.
However, a faulty pressure sensor is also indicated there for the excessively high pressure, while the line above indicates that this pressure sensor may be located in the engine control unit. I actually suspected the height sensor F96 contained in the fault memory. That too is definitely a pressure sensor, but could that be the one? Could it have such an extreme influence, especially with 1024 mbar, which I measured, is actually not that different from a real ambient pressure? If this pressure sensor is faulty, then a replacement of the engine control unit (ECU) would probably be necessary, right?