Hey guys, I know this is a common problem with our year cars. I'm still working on it. The moulding inside the rear door jambs-you have to remove it, 3 screws and 3 screws on the other. You will see holes drilled from the factory in the 1/4 panel. Those screws are supposed to be sealed either with rtv or some sort of gasket material. I sealed one side with duct tape, and it rained last night, no water in trunk.
So today, I insulated the moulding with butyl tape, sort of like strip caulk also put some on the threads of the screws. Will probably water test tomorrow. Will try to find pics to help understand.
Be patient. I'll find it.