Golf 3: Weak Performance / Power Loss

Hello,

I also experienced this power loss issue with my Golf 3 Variant 1Z, which had about 250,000 km on the odometer.
It first appeared 4 weeks ago.
"While I was pulling a trailer up a highway on-ramp, the acceleration cut out in third gear at 3200 RPM. I took my foot off the gas, and the problem disappeared (temporarily). It happened a couple more times, then I almost forgot about it."
Last week, the same tour, the same problem, but it started happening more frequently, in different gears and at different RPMs, starting from around 3000 RPM.
The problem exists even without a trailer. There's a loss of acceleration and a drop in speed.
No stuttering or wobbling.

Replaced the diesel filter while on the road (bubbles in the fuel supply line and it was old) -> no improvement, but the bubbles are gone.
Air filter replaced (old one too) -> no improvement.
LMM Pierborg cleaned with brake cleaner. Noticeable improvement; the problem only occurs above 4000 RPM. Acceleration is normal (8.4-8.7 seconds with 195/50-15 tires).
Diodentrick -> No change except for slower acceleration starting around 170 km/h. Limiting at 4100 rpm / 5th gear, with a drop in speed.
Boost pressure regulator replaced (I still have a cleaned one that had the wave acceleration problem) -> no change.

Garrett wastegate linkage sprayed with rust remover and moved approximately 15 times. Mass airflow sensor cleaned again -> okay (happy).

The likely cause was a combination of the mass airflow sensor and the throttle linkage. The maximum speed is now approximately 190 km/h (indicated by the speedometer).

Next, I'm going to purchase a diagnostic tool, which might also help me gather data related to the problem.

As a newcomer, I would like to thank all the authors who contributed to these discussions for their help, without which I would have been completely lost, and my only tool would have been my credit card.
Many problems are addressed, but unfortunately, it's often not explained how the problem was ultimately solved. Please don't forget this, even when you're happy that the TDI is now working.

LAMBDAPAPST

It's great that you were able to fix the error .

If the problem persists, you can try extending the wastegate linkage by half or a full turn. This worked for me. Of course, this requires that the pressure hoses around the turbocharger and the solenoid valve are leak-proof, and that the wastegate linkage moves freely.

Tom.