One of the girls who works in our office has a Chrysler Crossfire (I know
It has a rattling cat but passed the emissions test at MOT.
Because it has 2 pre cats and 2 cats and the way they are welded into the exhaust work, because one cat has failed she has to replace 3 of them. There is only one that is bolted on separately!
This, according to her garage, will cost £800.
My mate, who runs a garage, had a look and suggested the best way is to cut out the bad cat, stuff it with something, then weld it back in. Cost about £100.
It will pass emissions (as it already has) and won't rattle anymore.
Apparently, people do this all the time
I know what I would do.