PD-TDI: High Revs? Troubleshooting Guide.

Hello for now;

My girlfriend's Lupo, manufactured in 1999, with a 1.4L TDI engine (75 hp, AMF engine type), was tested today at the vehicle inspection station (using a Gutmann device).
According to the information provided, the maximum allowable speed should be 4700 RPM; however, I am sometimes exceeding this by approximately 35 RPM.
otherwise:
Top-quality, in the best sense - blurring, etc.

My question:
I've searched, but I haven't found anything specific.
The typical maximum engine speed for TDI engines is generally around 5000 RPM, as is commonly known.

-Is the above-mentioned speed setting correct?
-The tachometer signal is taken from the battery terminals. Are there any alternatives for the PD (Performance Data) system? (According to my research, this could be a potential source of error, and yes, it has been switched to a 3-cylinder engine).

-If this is indeed too high, how can it be fixed? No tuning, nothing at all, it can't be more original than this... (the only thing that's not original is a completely cheap exhaust system from IMASAF).

Regarding the vehicle itself:
Approximately 158,000 km, very low oil consumption (0.5 liters per 15,000 km), single turbocharger.

Regards,

P.S.: He eventually passed the ASU exam, but only on his third attempt...

Hey, what's the problem? The TÜV inspector just sets the maximum RPM higher, and that's it, right? Or is there more to it?

Hi,

He did, yes - he just didn't want to write it "loudly"...

The data is stored in the tester (depending on the vehicle/engine), including the target RPM. However, the actual RPM reading was not correct.
That's actually what worried me a little, whether it's actually "correct" or reliable.

I need to dig up those old ASU reports...

You can compare the engine speed by checking the OBD port.
I don't think it's that easy to adjust.