I also experienced some wierd and intermittent idle problems in my 84
Westy. I suspected a vacuum leak but could not locate one.  I then by
accident discovered the stud welded to the intake tube that supports the
bracket for the metal water pipe across the top of the engine had broken
loose taking a plug from the intake pipe.

This had obviously been broken for a long time as indicated by the
smoothness to which the break had worn.

I repaired it with a bicycle tube patch placed between the bracket and
tube and a hose clamp around tube and bracket foot as a temporary
repair.

Also I don't know if related, but on a road trip shortly prior to
discovery of the break
I only got about 7 milres per gallon for one tank of fuel.  Next tank
mileage was normal and has remained so for months now.

 Lance, hope this helps.