> This begs the question, as there were different series' of relays and valves
> and ECUs: Are there certain sets that were designed to go together?

For the 2.1 Digifant in NA, there's just the B revision and D revision
idle control module, and the only difference is the D revision is less
likely to crap out. ECUs for the NA market are likewise essentially
work-alikes, and really don't come into play anyway, as the idle
control system is completely independent of the ECU--- all it does is
watch RPM and allow more or less bypass air via the valve. Surging
idle with AC sounds like a bad idle controller, as it's the only thing
that's watching the compressor. A bad valve would more likely give you
a bad idle all the time.

--
John Bange
'90 Vanagon - "Lastwagen"
'90 Vanagon GL - "Wiesel"