Good old V8. The construction of the manifolds and catalysts shows that the engine is powerful and it was necessary to design slender pipes rushing backwards to fit in the engine compartment, but also to ensure the proper efficiency of the catalysts, it was necessary to place the catalysts right behind the manifolds. Sometimes it's hard to reconcile the two, has Audi succeeded? Yes and no ... As you know, catalysts are not eternal and over time they need to be regenerated, i.e. replace the cartridges with new ones. Unfortunately, the only option in this car to remove the catalytic converters is to remove the engine. Since the engine is on top, then on such an occasion it is worth to immediately, for example, replace the timing belt or other work that is difficult to access and requires removing the engine. In this case, one page was already blank. This is the result of driving with a damaged cartridge. A cracked or burnt ceramic insert wears out several times faster with each kilometer traveled than a functional one, and when it reaches sizes smaller than the diameter of the pipe that is behind the catalyst, it is spit out through the exhaust. In extreme cases, it can get stuck in the exhaust perpendicular to the exhaust outlet, blocking their flow. The other side didn't look too bad, but once the engine is on top, we do two. Two catalysts but four cartridges. Euro 4 standard according to vin no. The first two smaller - https://kat-eko.com/pl/uniwersalne/278-2025-wklad-katalizatora-uniwersalny-euro-4-awg.html#/45-srednica_wkladu-100_mm/57-norma_euro-euro_4/91-dlugosc_wkladu-60_mm and two rear larger ones - https://kat-eko.com/pl/uniwersalne/278-1423-wklad-katalizatora-uniwersalny-euro-4-awg.html#/49-srednica_wkladu-120_mm/57-norma_euro-euro_4/72-dlugosc_wkladu-80_mm.  Metal cartridges, resistant to gas, although there was no gas here and that's good ...

1. before regeneration

2. matching cartridges

3. after regeneration