badabing

There is a concept called exhaust reversion. Google at your own risk.

ajw45

This. Search is your friend.

Schroedinger

This has definitely been a problem on some other motors, notably the 1zz in the Toyota MR2 Spyder. I’ve never heard the theory applied to Porsches though.

WAILN6

It actually happens in aerospace facilities with nitrogen lines. It’s counter intuitive but fluid dynamics can create an eddy along the pipe walls and contamination can move upstream. Never heard of it happening in cars, but the physics can support it.

Tmc981

Regarding the OP's original question:

EPA regulations dictate that factory installed catalytic converters last 8 years/80,000 miles. Replacement cats are required to last 5 years/25,000 miles. All carry warranties to that effect. Assuming that an engine is maintained properly and the car is driven in a manner that regularly gets the cats properly heated so that the requisite chemical reaction can occur, factory cats can and do last for the lifetime of a lot of cars.

While the exhaust reversion phenomenon definitely exists, it takes specific conditions for it to occur, conditions that typically don't occur in a properly tuned Porsche street engine. I am not a technician, but in my 50+ years of hanging around and working on Porsche cars, I've never heard of a Porsche doing this. Actually, until reading this thread, I'd never heard of it at all. That doesn't mean it can't/doesn't happen in Porsche cars, but I think we can assume it's a pretty rare occurrence.

Things most likely to "kill" a cat include short trip cars that rarely get the cats properly heated and poor engine tune/condition that allows raw fuel and oil to be pumped out of the cylinders directly into the cat. Recently, I helped my grandson with a bad cat on his 130,000 mile Jeep. In the end, the diagnosis was that a bad plug wire caused a misfire that enabled raw fuel to get to an already aged cat which then proceeded to plug itself. Sadly, a $35 set of plug wires would have delayed an $800 repair, for a while at least.

I would think that if the OP's car has been kept to spec tune and has been driven at intervals that include proper heating of the cats, there is virtually no chance of a cat failure that would result in bore scoring due to exhaust reversion. In fact, there are so many other things that can go wrong on these cars before exhaust reversion, I wouldn't even think about it again.

Finally, cats are there for a fairly important reason and are part of the tuning spec for these cars. I get the "sound of power" thing, I really do, but removing cats isn't always the better course of action.

Drive your car...
Terry