Not bad for a wild guess. The Haynes manual for my daughter's '93 Accord has
a nice test for exhaust restriction:
*connect a manifold pressure guage to the intake manifold
*start the engine and open the throttle enough to bring the rpms to about
2000 for a few seconds
*suddenly release the throttle and watch the guage
If the guage returns to approximately the idle reading within two seconds,
the exhaust is clear. If the guage hangs around the 2000 rpm reading for a
couple seconds or returns to the idle reading very slowly, the exhaust is
restricted. Note that the restriction can be in the cat or in the muffler,
and taking things apart is the only way of telling where it is. We had an
'82 Toyota that had a melted cat, and when we got it off and tried to blow
through it the restriction was as bad as you'd get from a soda straw. The
engine started and idled okay, but didn't like to rev and spit gasoline
spray out the carburetor when the throttle was opened.

Mike

This happened to my mom's '86 240 years ago, it was rattling like crazy
for months, I pulled the cat and dumped the broken bits out and put the
empty shell back and haven't touched it since. Amazingly the emissions
test still comes out very well, great engines, very clean burning.