'89 200T: Low Oil Pressure warning

[Barton Oleksy]

I'm talking about the computer display of an oil can, which the manual
says is a warning of low oil pressure.

We had this on the '89 200T about 2 months ago or so - only happened
when the engine was warm, and only when idling (say at a stop light) or
perhaps as we would come to a stop.  Local shop replaced an oil pressure
switch of some kind, and the problem went away.

NOW IT HAS RETURNED!  Same local shop confirmed replacement of this
switch (with a new one).  Asked about oil, figured it was probably still
5W30 from winter, so they did an oil change to 10W30.  Problem *seemed*
a little better at first, but now is still doing the same thing.

If I come to a stop but pop it into neutral and keep the RPMs up a bit
(means braking with left foot - yikes), the light doesn't come on.
That's no way to drive, of course.

Local shop thinks maybe the dual oil sending unit (I'm just passing this
along, don't know more details than that).

Another shop thought there were TWO switches (one ground, one open) so
it could be one of those, maybe only replaced one earlier...?  Or else
something more major like the crank bearing is no good or missing or
something...which means a pretty big repair job, apparently.

Any other thoughts?  Or more details needed?  Thanks for any and all
advice/suggestions...

Bart
'86 CGT
'89 200T
'91 200Q