jonathan:

Sounds like you have an after-market (non-vw part) weber progessive
carberator set up.  check the regular vw rags to see if you can spot
your set-up.  It's prolly a rectangular filter (two metal plates w/ a
paper filter-type sandwitched in betwix).  These filters are obtainable.
Most likely through mail-ordr unless of course u live in cali.

christian