Make sure to seal up the body crimp on the outside ot the trunk seal ( factory defect ) Its a mystery leak that not to many people know about.
You would be amazed how good GUNK ADHESIVE REMOVAL in the bright yellow can loosen glue-like material if you let it set for a minute or two!
ALSO Replace the Molding at the trunk site> On the photo you can see holes where water can get in also unless sealed as well.
When done have a friend put a sprinkler to the car while you are in the trunk watching for drips
P.S Make sure he is a GOOD FRIEND so he wont pull a fast one and leave you in the trunk