No idea if this is typical or not since I'm not sure just
how cats. are assembled at the factory. But my guess is
that the front honeycomb slowly disintegrated and filled
the front of the back honeycomb section until the process
accelerated and clogged the rearward section completely.
Does this sound like this could happen?
Bruce
'86 Spider '73 GTV
Yep. Happened to me twice. Don't know how old your broke aftermarket
cat is/was, but cats seem to be better now - go get an approved cat,
and enjoy ( they are also much better at flowing than 10 years ago...
)