These come from the latest issue of Import Service, May '96:

Bucking engine, irratic idle and performance:

Several Porches have been seen with torn intake air boots, torn in 
the area between the air flow meter and the throttle body. This can 
happen very easily with Vanagons as the engine mounts allow a lot of 
flex and the air cleaner is firmly fastened to the body.  As the 
engine rocks, the cracks open up and admit 'false' air which can cause all 
sorts of nasties.  Check the intake boot very carefully for a split 
or deep crack.

O2 sensor wires:

As Gerry Skerbitz found, the O2 sensor wire is actually a co-axial 
wire and subject to shorting out between the conductors and giving 
the engine fits.  A common cause of this happening is piercing the 
conductor with a needle-point multi-meter lead to get a quick 
reading.  The poking of the co-ax with a point pushes the co-ax 
shield down into the center conductor and shorts out the O2 sensor 
signal.  Who pokes these wires?  Your friendly local garage or VW 
mechanic as it is easier than back-probing under the connector boot.