You know what, you're right.  My bad.  I have only seen the B or D and just
assumed they were date sensitive since the B is always on '87 year vans and
the D is always on the later model vans (my 91).  But I have never seen and
A, C, E, etc numbers.  Right now if you went to buy a new one you should only
be able to get the D unless someone has some NOS they are trying to get rid
of.  However they should be interchangable (I have interchanged them with no
problem).

Sorry about the confusion.  I have both the idle stabilizer valve (PN 025 906
457A) and the idle Control Unit (PN 251 907 393D) available for $240 each if
anyone needs them.

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
Phone: (856)-765-1583
Shop:   (856)-327-0027
Fax:     (856)-327-2242