I don't know if this helps but with my 90 GS, the water comes in on the driver and passenger side, because the windows are not framed (free windows) and when the door is shut it doesn't meet the door seal tightly. It's not visible to the eye, the gap, but i was able to feel dampness on the door panels. My floor areas on the driver and passenger side get damp and it smells. I think also the water goes underneath and is absorbed by surrounding areas.

But... my hatch always gets foggy and i have found condensation back there but cannot seem to find a leak in the hatch. I don't know enough where to look.

Now that I have read this I will also be checking the sunroof drains. Whereabouts are they/should I look?