I drive an '86 Syncro.  Can the vibration related to u-joints on the
front/rear driveshaft come and go.  I have a vibration such as described
(mostly between 40-50 mph) only about half the time.  May it also be in the
suspension, as it sometimes seems to be related to the road - it often is
present over the same stretches of roads, and gone over the same other
stretches of roads.  The tires are new MXTs, and the shocks are new.

I also have a recent problem with my A/C.  It was doing just fine until
about 2 weeks ago when it started to not get so cold,  This is getting
progressively worse.  The system is cycling properly, but doesn't stay on
very long although it is not getting very cold.  I just had Freon topped up
(added 1 lb) and the system pressures checked (46/300 psi at idle, 33/330
at 2,000 rpm).  The system seems to be charged, and the compressor and
expansion valve working well.  But the compressor doesn't stay running for
long.  Also, the air coming through the ducts seems humid to me.  Is this a
diagnostic clue?  i live in Las Vegas where it is quite dry.