Sounds like your fuel pump. To check, listen to the aluminum cylindrical
thing underneath the van about midway back, closer to the passenger side.
There are a number of things that could cause this but it is usually related
to restricted flow. You might need a new fuel filter, for example. (Cheap,
easy.) Search the archives on "fuel pump" and you'll find a ton of stuff.

Geza

"As an incidental, whenever I start the van, I hear a high-pitched, low
volume sound for about 30 -60 seconds.  The van runs beautifully, and I
don't notice any problems at all.  The sound will go away by itself within
30-60 seconds, or if I press the accelerator.  Is this sort of thing normal
with Westies, or should I be getting something checked?"