Muffler broke?

[John Chia]

Hi Guys,

I have some nasty rattling sounds coming from my tailpipe.  It is
loudest at the outlet of the muffler.  It's so bad, it sounds like a
Honda motor from 3-4k RPM.  One mechanic thinks it's the cat rattling,
another thinks it's the muffler's guts.  It's a stock 200SX muffler with
a 2.25" midpipe leading to a hotshot header through the engine into a
AEM CAI.  It was also happening with the stock intake that I had on
recently.

Would it be possible that the muffler's baffling (or whatever) broke up
and is rattling inside?

TIA-
John.