Aircooled Chris:

There were California and non-California models
in '81.  The non-California model had a pretty
straightforward exhaust/heat exchanger layout
with EGR.  The California model had a much more
complicated path for exhaust and used an O2
sensor just ahead of the cat and did not use
EGR.  (The non-California model also used a cat.)

I don't know if the currently Bentleys show this,
but the '80-'81 VW manual (pre-Bentley) has it
all clearly pictured.

                        Richard A Jones
                        Boulder, Colorado