One of the things I found out about with Darrell Boehler's Digifant
tool is that the throttle switch (TS) cuts the fuel injection at a
certain RPM to allow engine braking.  There's a big difference
between coasting down hill with your foot cracking the throttle just
enough to turn the TS off and having the TS on.

If your van is sputtering and backfiring down a hill with the foot
off the throttle, your TS is probably maladjusted or the switch arm
is bent.

-Karl

Karl F. Bloss - blosskf@apci.com or bloss@enter.net
'87 Vanagon GL Weekender "Beverley"; Trexlertown, PA
http://www.enter.net/~bloss/vw/
Busses by the Trail: http://www.enter.net/~bloss/vw/bbtt/