Yep, this is a known issue with the cats. Old age more than miles can cause them to do this. I have Larini High flow Cats in stock and also cat delete pipes. These were just fully redesigned with Inconel and I have the latest version. Call me if needed, etc.Fairly uncommon. The OEM Cats can degrade and parts can get sucked back into the engine causing damage. I think that's about it for preventive things to be worried about with the engine internals. You could have a problem but it's pretty rare.