so a week or so ago i had the chance to take apart a 1.9 wasserboxer
exhaust with the factory exhaust system on it.  or i assume it was since
the van is from arizona.  anyhow the exhaust nuts mounting the headers to
the heads were unlike any that i have seen before.  they are 13mm nuts
with what look like wound spring steel inserts inside them.  similar to
what a helicoil looks like.  if these are factory nuts are they still
available at the dealer or would the dealer hand me some regular nuts with
a N part number?  additionally does anyone know why these nuts were made
like this?  i would guess something to do with the thermal expansion
differences between the aluminum head and the steel of the header and
stud.

jonathan