'93 90 dash rattle

[Elliott Potter <epotter@abraxis.com>]

It only now occurred to me that I still hadn't asked the experts about
my dash rattle!

I have a '93 90CS, and it has an incessant rattle that comes from the
driver's side area of the dash (that's the left side).  The dealer went
for almost 2 years not being able to hear it.  Then one day they
replaced the speedometer, saying the speedo head was faulty.  No dice. 
Then they said some A/C hose or other was rattling, so they insulated
it.  No dice.

It rattles most when it's cold (or at least not *hot*), and seems to go
away as the engine heats up.  It definitely rattles when I hit a bump or
anything like that.
It seems to be coming from the area of the speaker in front.  Any
suggestions?

TIA!

Elliott