as promised here are the pictures of an OEM Porsche catalytic converter and a high quality, aftermarket, metal 100cpi cat. Both in the same OEM housing.

You can see how big the difference in possible flow is and also it can be seen how it is welded into the housing. From the outside there is no difference visible. As the new metal cat flows much better, it is also louder.

OEM Porsche:
http://forums.pelicanparts.com/uploa...1471404365.jpg

modified 100cpi:
http://forums.pelicanparts.com/uploa...1471404395.jpg

Wow, more details please or a link, Can one get this in the U.S.?

unfortunately cannot help here. It is a very common modification in Germany, but there is only one company doing that mod using the high quality cat and installing it in the OEM housing (so that smog in not an issue).
I understand that there are aftermarket complete catalytic converters available but I never looked into it.

The same company doing the mod also sells a complete converter in a new stainless steel housing, it is however pretty expensive and no reason to go that route.

:: DW Auspufftechnik - Produktbeispiele die Marke Porsche

I have no affiliation with that company, just had that work done by them and as said they have a very good reputation. In the meantime I have moved to a much better overall exhaust setup and that is coming from a different company.

I see no reason why somebody in the US could not do the very same.