I recently purchased a Turbo Muffler from S & S (602-847-9000).

S&S manufacturers a top quality Turbo Muffler and tail pipe combination
for Vanagons.  I put one on my 1984 H20Boxer and, while slightly more
noise, gas milage improved by at least 1.5mpgh.  Better yet, the total
cost is less than the replacement anywhere!!

They also make headers that are high quality and reasonably priced, much
cheaper than replacing all of the broken Volks header pipes.  Allows for
converter to.
If you call mention Davidb and you'll get a discount.

davidb