clunk gone, rattle persists

[nde264 at lulu.it.northwestern.edu]

Car in question is a 89 90q.

As per several listers' recommendations, last weekend I removed, cleaned, and
reinstalled the brake booster vacuum pump.  The clunk that I had observed
disappeared, but there was still a rattling noise.  I then removed the
actuating rod for the pump, still a rattle, but no noticeable braking
difference, so no more clunk for good.

So, I have a rattle coming from what SOUNDS to be in the top front part of the
engine.  I haven't listened from under the car, so it could be coming from the
bottom.  The rattle is there at idle and increases in frequency with rpm
increase.  The rattle also doesn't disappear/reappear when the car is
cold/warm, it is always there.  The rattle *seems* more pronounced when the car
is warm, has sat for a few minutes, and is then restarted.  The car idles well,
and runs fine through the whole rpm range.  The rattle doesn't seem to be
affecting performance.

Also, there is a clicking coming from a little ?valve? coming off/in series
with a brake line near my battery.  What is this part, should it be doing that?
 Sounds kind of like a lifter ticking.

I checked the archives and could only find mention of a worn distributor gear
causing a rattle, so I'll check for play in that at lunch.

Any ideas, suggestions for where to start?  Water pump, PS pump, etc?

TIA,

Nathan Engelbert