Paul, it sounds like everything is good except that the tach wire is either
not there or not hooked up.  I would just run a wire from the coil ( number 1
terminal (negative)- wire should be green already).  Run that up to number 9
pin for the plug.  

If you look at the plug there are numbers stamped on it already so finding
which one is number 9 is just a question of looking at the plug itself (also
you will find that if you remove the black plastic plug housing on the
instrument cluster that on the foil circuit, they have actually printed a
number and the name of what each pin is for- thank you VW!).  I would get
some green wire from Radio Shack in 25 ft roll, put a spade connector on one
end and plug it to the coil.  Then hook the other end to the number 9 pin and
your tach should be good to go.
Hope this helps.  Sorry I didn't get back to you yesterday, but I had another
round of computer crash blues (everything is fixed now).

Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242