Hmmm... interesting note on that alternator correlation...
John, I too have a 16v ('87) and my gas gauge was intermittently flickering when tank dropped to around 1/3 or so. But I haven't noticed it lately.
Here's the interesting part that I would never have associated with this: I just had my alternator replaced last month (f'n $465 later I'm now all set!).
While I'm no electro-genius, I haven't seen the gauge flicker since. Maybe there is a correlation? I'd say follow Chuck's advise, can't hurt to get an output test. Good luck! (and go see the 2.3-16 survey thread if you have yet to sound off!).