Need a "donut" gasket for the downpipe/cat flange

[Peter Schulz]

Folks:

I'm have to replace a stock rattling catalytic convertor with a "loaner" from Chris Miller ( thanks Chris!).

The local garage owner has offered to let me use his lift for the R&R.

Of course I want to have the donut ready _before_ I cut off the old bolts at the downpipe/cat flange.
Does anyone know what size and type the donut gasket is, and whether I get just get one from a foreign autoparts store or am I stuck buying oem from Audi?

And while we're at it, what size grade 8 bolts?

Thanks in Advance!

-Peter
Peter Schulz
1990 CQ
1991 200 20v TQW indigo mica
1991 200 20v TQW titanium grey
Chelmsford, MA USA
peschulz at cisco.com