Gregor
By drop rpms to zero do you mean your tach drops to zero and the van
stumbles then recatches and drives on or does it stumble but the tach
still shows diminishing then recovering rpm?

  If the former, you have a temporary loss of ignition. ( The tach is
triggered by ignition circuit pulses.) Look for damaged wires,
grounding points etc.
  If the latter, it's a fuel delivery system problem.

Check the filters again. You may have a nasty filthy tank ( or got a
load of dirty fuel- possible if you filled up while the stations
tanks were being or were just filled- turbulance in the tank stirring
up any sediment) and the filters are clogging up again.

  Goood luck.
On 19-Apr-07, at 10:19 AM, Automatic digest processor wrote:

> Date:    Thu, 19 Apr 2007 10:11:25 -0500
> From:    Gregor Brandt <gbrandt@MARIONETTE.CA>
> Subject: Stumbling after fuel filter change
>
> '86 Westy
>
> I've written about this before, but am having troubles fixing it...
>
> My van would suddenly drop RPMS to 0, for an instant, before coming
> back
> to proper RPM, causing severe bucking.  After looking at the usual
> suspects I checked the fuel filter and it was filthy.  Changed both
> the
> plastic fuel filter pre-fuel pump and the high pressure filter post-
> fuel
> pump.  Van stopped bucking, but now it stumbles under load.  It
> never did
> it before.  It has to be fuel related, but I have no idea what it
> could
> be.   Any help is appreciated.
>
> Thanks,
> Gregor