The cat on my 380sl was plugged because of a valve stem seal issue.
So I temporarily replaced it with a straight pipe, just to see what
the effect would be, at least until I can get the seals done. Voila!
The car is now far more responsive than it ever was, and I'd venture
to say that it has 15-20% more power than before. However, removing
the cat made the car noticeably louder.

I only drive the car occasionally, and it's registered as a classic,
which doesn't have to pass emissions inspections. So I was thinking
about replacing the cat with a second muffler  to hopefully muffle the
sound without robbing the car of its newly found power, as I suspect a
cat probably would.

I was therefore wondering what the pros and cons of doing this would
be, ideally without getting into a long discussion of the associated
environmental issues.Thanks very much is advance for any advice anyone
can give me on this.