Considering the relatively low mileage, the catalytic converter was very damaged. Initially, I thought it was an oil defect, but the culprit turned out to be a leak in the exhaust manifold, which in this model is liquid-cooled and connected to the head through water channels, and is also integrated with the turbocharger as a whole. The water and exhaust gas mixture went straight to the catalytic converter. A layer of scale has formed on the catalytic converter, significantly blocking the flow of exhaust gases and reducing the efficiency of the catalytic converter. It was the last moment to replace the cartridge, because the GPF filter, which is located behind the catalytic converter under one housing, already showed slight traces of the impact of a collector leak, but was only slightly dusty. It was enough to remove the scale, clean everything thoroughly and weld in a new catalytic converter insert. We always use inserts with dimensions that match the originals as much as possible and in this case it was an insert with a diameter of 130 mm and a length of 100 mm. Of course, an insert with the Euro 6 emission standard, because this is what the VIN number requires, and an insert with a lower standard will not work, generating a catalytic converter efficiency error, most often with the code P0420. We weld also to the customer. This time I managed not to cut the pressure tube after several previous regenerations of the same catalytic converter and I received insults from Przemek J (the welder) - why are you cutting these tubes, how can you only cut the tube mountings and deflect it? Actually, you're right, learning doesn't go to waste and that's what I did ;-)

Catalytic converter insert used for regeneration - https://kat-eko.com/pl/uniwersalne/390-2415-wklad-katalizatora-benzyna-awg.html#/37-dlugosc_wkladu-100_mm/51-srednica_wkladu-130_mm/59-norma_euro-euro_6/65-przepustowosc_cpsi-600

Original OE catalytic converter numbers:

18328685235

18328684906

1121521201000