In a message dated 1/12/00 6:29:57 AM, KENWILFY@AOL.COM writes:

<< << The part number on the stabilizer in my vehicle is 251-907-393B. This
part
 number does not match the number i found on the BusDepot web site for a 1987
 model. Is this the correct part number for my van? >>

This part number is the correct one for an '87 Vanagon.  Basically they are
all the same and interchangeable on the 2.1l engines (I have done it so I
know).  The number is the same for all the 2.1l years: 251 907 393.  The last
letter is date sensitive.  A is for 86, B is for '87, etc.  It doesn't effect
how the stabilizer works, just when it was made.
 >>

In my experience, on Vanagons from 1986 through 1990, I have only seen 2 part
numbers for the IDLE STABILIZER CONTROL UNIT: 251-907-393B and 251-907-393D.
I have been told by the local dealer that the 'D' part number supersedes the
'B'.  This being the case, VW is stating that the 'D' part can be substituted
for the 'B' part.  As far as using a 'B' in place of a 'D', the only thing
that I know for certain is that they both fit the same mass connector.  I
doubt that VW revises its part numbering solely to track the date of
manufacture, especially since such things are normally done by imprinting the
part with a date code.

There seems to be a problem with terminology here.  The IDLE STABILIZER is
the solenoid valve which sits atop the engine and shunts the throttle valve.
The IDLE STABILIZER CONTROL UNIT (P/N 251-907-393B/D) is the 'black box'
mounted in front of the right tail light.
Unless they have lied to me, The Bus Depot does not stock the IDLE STABILIZER
CONTROL UNIT only the IDLE STABILIZER.  This must be why it does not appear
in their parts listing.

Richard