Between 37 and 42 seconds per the FSM

Definately not the ELC, it sounds perfectly normal.

I am not a pro so correct me if I am wrong. I have heard a bad cat that was junk sound like a muffler draging. When the stuff inside breaks up it sounds like rocks in a coffee can. This could be a possibility. If you lay under the car and pound on the cat with your fist it should make the same noise if this is the problem. Then you have a reason to put on a high flow cat.

Are you sure it'* not a rattle that sounds like a grinding noise? Maybe a heat shield is loose...

I'll check both those out in the morning once the exhaust has had a chance to cool down.

I'm kind of thinking along with the exhaust guys at this point, but further back.

Our '98 is famous for very annoying, hard to find noises in that boxy area containing the last of the exhaust pipe and the muffler. Even at rest (if clamps and/or hangers have deteriorated), engine vibration at idle can easily work it'* way down there.

Might as well look closely while you're under there, if you haven't already.

I'll examine the exhaust thoroughly while I'm down there... I've not climbed under there since I first bought the car, so I'll do that tomorrow.