"The" stuff you want is called Stabilant.  It was used by VW on the
electrical connections at the factory.  Unfortunately it's not cheap,
but it has the interesting property of both enhancing conductivity of
connectors but being non-conductive between adjacent connections in
multi-contact connector.

I read about it here[1], the VW part number is supposedly  ZVW 186 001
STABILANT 22A

Allan

[1] http://members.tripod.com/~fuelie/tuneup.htm

--
1991 Vanagon GL