OK let me clarify the clarification.  The exhaust system I sell is made by S&S
headers in Arizona, USA.  I am a dealer for them and sell their stuff at a
discount.  The performance exhaust system for the Vanagon consists of a 4 to 1
header ($160) which attaches to your stock VW Vanagon Catalytic convertor.  On
the early 1.9l header there is a provision for the oxygen sensor in a similar
location as the stock exhaust (the 2.1l oxygen sensor goes in the cat so there
is no provision for it in the 2.1l header).  You can then either bolt your
stock Vanagon muffler and tail pipe up to your cat or you can get a "turbo"
muffler that replaces the stock muffler and tailpipe ($120).  So these pieces
are totally interchangeable with the stock stuff.  You can get the turbo
muffler and bolt it to the stock exhaust system or get the performance header
and bolt the stock cat and muffler up it to.
These pieces come with the necessary gaskets and hardware for installation.
No welding or anything like that is necessary, it is totally bolt up.
The prices for the header and muffler are the same price for the 1.9l Vanagon,
and the 2.1l (which includes the Syncro) $280.  The parts come with a one year
warranty.
Specs are:  1 1/2" diameter steel pipes(16 gauge), with thick CNC plasma cut
flanges.
As for noise pollution, I am sure that the more freer flowing turbo muffler
has a different sound than the stock muffler but it is below DOT standards for
noise so it is not loud.
I guess that answers all the questions I got so far.  Sorry about the
bandwidth.
Ken Wilford
Van-Again
John 3:16