I do. I just had my 1993 90 CS driver side Cat changed. Your engine
control unit is not happy that it can't get rid of exhaust. Your car
will eventually crawl to a halt. However, Audi Service guy told me
that engine computers are smart enough to know when to shutdown and
you don't damage anything.
I would advise not driving the car if you can.
New cats will make for a new car!