Peter
Do a leak down test .
To see where the compressed air is going ,after turning the engine over to get
compression use an old stethescope to listen for leaks.
some listening points are the oil dipstick hole , breather on top of the moter
(the one that used to be a generator stand on a beetle) and at the valve cover
also around the exaust .
this will at least point you in the right direction before you start on all
the expensive solutions

mike
85 westy 215k