If your gas millage is not falling off, and you are not having issues at idle you may just be ok. First sign of trouble on Inga (86 245DL 237K)was when I passed Nox by five points, not even close to failing the year before. Then started having running issues when the engine was cold that went away when it warmed up. Noticed that the problem got better or worse going over bumpy roads in the morning (never ending road work by the house). You could hear stuff rattling around in there after it was removed.

But before you do anything drastic, you may just have a loose heat shield on top if the converter. You can roast stuff on the back passengers side floorboard without that on there. If you are just hearing a metal rattle there is one old trick you can try. Get a couple of large size hose clamps and put around the heat shield and around the bottom of the converter. Rat down tight and see if that makes it livable. Cheaper that a new cat, at least the metal automotive type. If you only need to replace the cat not that hard to replace. The muffler behind the cat on the rubber doughnuts still has me traumatized. But the cat was not hard.

Good Luck,

Paul