Before you go buying new parts, check the plastic vents on each side of the trunk. They are known to pop out of place, letting in water. They usually will pop back into place with a little effort. I also found out when trying to correct the sagging(for lack of a better description) on the sides of the bumper, that if you shove a tennis ball in between the bumper and the vent, it will fix the vent problem, as well as the bumper sag.
