[HLandin]

I had a similar problem with my white '90 9c1. Problem fixed itself when I replaced my CB mount with one that better fit the hole (I think it sealed better). Anyways, after the change, no more moisture problem in that car until I lost it in the accident. So my guess would be, there is some kind of leak which allows the moisture (or moist air) into the trunk and allows it to accumulate and condense.

If it is a leak, it may not be the gasket. A '89 Caprice 9c1 I was looking at lately had the same moisture problem in the trunk, but the gasket was in perfect condition, so the leak must have been somewhere else from what I can gather (although I couldn't figure out where).