Check Catalytic Converter: Symptoms & How To

Hello.

How can I be sure that my Audi A3 1.9 TDI catalytic converter with 178,000 km is worn out?

I've been experiencing fluctuating performance issues for quite some time now, sometimes more severe, other times less so.
After driving at full load, it's usually better, but the turbo seems to be somehow restricted from reaching its maximum boost. Sometimes the turbo doesn't kick in until 2100 RPM, and other times it's at 1800 RPM.
My A3 is chipped, so it should be fully running at 1500 RPM.
I've also logged data on several occasions and noticed that the boost pressure simply cannot be built up at low engine speeds. There's a significant difference between what it should be and what it actually is.
At a temperature of 1600, the maximum pressure should be 1950 millibars, but it is actually around 1300-1400 millibars.

Can someone help me with something?

It sounds more like a stuck VTG (Variable Transmission Gear) to me.

Have you looked at the technical articles and worked through the error checklist?

If you can rule out issues like a blocked catalytic converter, insufficient vacuum, a faulty mass airflow sensor, or exhaust leaks, then it's possible that your catalytic converter is defective or clogged. You could try briefly removing it (by disconnecting the exhaust pipe between the turbocharger and the catalytic converter) to see if that resolves the problem. It won't be extremely loud.

If it's a cat, you can decide whether to remove it (which is not allowed) or replace it. Otherwise, search for relevant articles systematically.

"Come on, you wouldn't want to drive recklessly, would you?"
If the catalytic converter fails, I would install a diesel particulate filter (DPF). This is the perfect opportunity to do so!
"For that to happen, the original cat needs to be removed."
But if the cat lets something else through, all the better.

How would an empty catalytic converter affect performance (keywords: back pressure and cross-sectional area)?

At the very latest, it would be over with the next scheduled maintenance period, right?

Even though it's been a year and there's no solution yet: Removing the catalytic converter results in the revocation of the operating permit. If there's nothing left inside the catalytic converter (which apparently can happen), it shouldn't affect the emissions test... It's not just a "smog catcher," but helps with the reaction of the gases... But what exactly is being measured during the emissions test for a diesel engine?

kossmann wrote:

How would an empty cat actually affect performance (keywords: back pressure and cross-section)? At the very latest, with the next scheduled maintenance period, it would be over, right?

In a turbo engine, the absence of a catalytic converter will naturally have a positive effect. This means that the turbocharger can rev up more easily due to the reduced back pressure.
The A-scan test shows nothing abnormal because it only measures the cloudiness, which is not related to the cataract.

The proportion of pollutants is already significantly lower in diesel engines compared to gasoline engines. However, due to the non-homogeneous air-fuel mixture, diesel engines also produce additional particulate matter, i.e., solid particles (mostly soot), and components that exist as condensate.