Donna:

Real Vanagon syndrome, which surfaced a while after the 2.1 was
introduced, is cutting out after long sustained highway driving at a
steady speed.  The cutting out can also be bucking.  A restart
cures it, until it comes again.  It is a problem with the signal
coming from the AFM when the vane stays in a fixed position for
a long period of time.  The VW pigtail or home-made fixes with
a capacitor cure it.  The restart cures it because of the power
off/on to the ECU.  I think real Vanagon syndrome is much less
common than applying the name to another problem.

 From your description, you MIGHT have Vanagon syndrome.  If so,
a pigtail will solve it.  If not, checking wiring is the right
thing to do.

If the tach drops to zero when the cutout occurs, suspect the
Hall sender in the distributor.  The sender plastic can crack
where the wiring exits and there can be a break in the wire
that comes and goes.  Your description matches what I remember
when my Hall sender went bad.  The tach is driven off this
wire, so that is why it drops to zero when the sender cuts out.

Good luck,
Richard