1989 300 SEL Center Muffler QUestion

[outofspec]

I'm new to this forum, so hello to all and thanks fo ryour help.

I replaced the center muffler in my 1989 300 SEL today. It was a long dirty job, and all seemed to go well except for one thing.

The connection between the Cat and the center muffler is leaking badly. The guys at Performance Products sold me two of those exhaust seal rings, one for each pipe. The one pipe from the Cat that extends into the center muffler pipe seems to be sealed well. The other pipe that has a metal type spacer beteen the Cat pipe and the center muffler pipe has blown out that exhaust ring seal. Is this pipe even supposed to have a seal ring or is it? Or is it simply a metal to metal crush type fitting.
I would appreciate anyone who has done this job or knows about it clueing me in.

Thanks!!