another howling 5kS, and other questions

["G. Benedikt Rochow" <rochow@segosf.hlo.dec.com>]

(car is an '84 5kS non-t non-q automatic)

-Just a few days ago, I started noticing a slight, quite low-freq.,
howl at speed (audible above 40 mph, I think - need to do
some diag. driving) whenever the steering wheel is turned
noticeably right of center. Diff?

-a few days after having the timing belt and pump done
(and cam (?) seal replaced, upon mech's opinion that it needed it),
I started noticing that quite often (at idle and only when in P or N)
there is a pulsing (1-2 Hz) mid-freq. metal-on-metal sounding squeal/howl.
Also, possibly unrelated but starting at the same time, I occasionally
get the auto-check oil pressure warning light on for maybe 5 secs after
starting. This happens maybe on 1 in 20 starts (all cold, I think).
...though yesterday, I got it a second after turning the key to 'on',
and not yet starting - it turned off when (or before) I actually 
cranked it.

-somebody (Phil?) mentioned long-term unnoticed-by-owner
lack of vacuum advance. What is it, how can I tell if
it's not working, and what will happen if I in fact have
a defect but don't know it?

TIA.
-gbr