> I recall seeing the instructions for a little tester that can be built
> with a Digikey panel meter, and some other bits and pieces, which can be
> connected to the Vanagon engine and, using a knob, allow monitoring
> various sensor voltages, such as the O2 sensor, etc.

Daryl Buhler:
http://www.loam.org/vw/Vanagon/DigiTool/