Darrell has posted several notes to the list about his tool for
troubleshooting the digifant fi system.  Basically, what Darrell does is
solder a cable with a  inside the ecu, with a female connector on the other
end.  He then constructs a box with a male connector which plugs to the
aforementioned female connector.  The box contains electronics supporting a
series of led's to check various engine functions and a pin layout that
allow one to check the oxygen sensor, afm, and both temperature sensors
with a multimeter- and do it while the engine is running!  Detailed
descriptions of the electronics are on Darrell's website at
http://taos.midwest.net/vw.

Darrell lives in southern Illinois, about three hours away from me.  I was
so intrigued by his idea that I made a trip down there and watched while
Darrell made the connections inside a spare ecu I had. (I also enjoyed the
hospitality of Darrell and his wife Jolene). He had already assembled all
the electronics for me (and charged me only $50 for everything).  Since
then, I have been able to troubleshoot three vans that were running so-so,
but not great and found what was wrong with each of them in less than five
minutes.  Doing all the checks per the Bentley would have taken hours. 
Some parts of the digifant system can't really be diagnosed without the
engine running (the afm is a good example) but are a snap with Darrell's
tool.

While I used a spare ECU, the modification is benign enough that I am not
worried about it damaging the ECU.  In fact, I now keep that ECU in the van
I drive most often, removing it when I want to check out another van.  This
way I know I can instantly diagnose any problem that comes up on the road. 

I can't overstate how much of a boon this tool has been for me.  I'd
recommend anyone owning an 86 or newer vanagon to check out Darrell's
website or contact him at: midwesty@taos.midwest.net. 

Bill
www.geocities.com/yosemite/gorge/1706