Hi!
I have a water problem in my trunk as well. Itīs a 95 Riviera and water seems to come from the left top corner of the trunk. Iīve been driving w/o the carpet for some weeks to locate the leak.
It drips from the screws that hold the lid, but thats not where water comes in.
Further to the front end (upper left) of the trunk there ist an opening with insulation material. This stuff is soaking wet! I wonder if water could run all the way from the sunroof...
Do you have a sunroof (astroroof)?