Hi Chris:

I have an '86 244 that also leaks into the trunk after very heavy rains. I have traced my leak to a leaky taillight assembly. Do everything all the other guys have suggested, but also check around your taillight assembly gaskets to make sure that water isn't coming through there. Then check to see if there is water in your taillight lenses. This is where my problem was. The water would leak down into the taillight lense and seep through the holes for the bulb assembly. I have tried to seal the visible cracks in the lenses (I have used clear nail polish) and have drilled the obligatory holes in the bottom of the affected lenses. Someday on my list of things to buy is a used but not cracked taillight lens (all of the 240s at the local salvage yards have had their lenses pulled already). Good luck with the leak finding.