Here's the fix...
The part number is F5RZ54280B62A. It's called a grille. It's not too much
work. You need to remove the plastic piece covering the trunk lock area
and then remove the carpet on the side of the trunk. To get the plastic
piece off, you need a phillips screwdriver for the four plastic screws (be
gentle with the screws). There are also two plastic pop rivet things you need to
remove. The carpet is held in place by a plastic screw and two plastic pop
rivets. Once you remove the carpet, you will see the black plastic vent that you just bought. Remove the new gasket from the new vent; unfortunately, you
don't use the new plastic vent because you'd have to remove the bumper to
install the whole assembly. The vent snaps into the sheet metal. Remove
the old gasket from the old vent, clean the vent and sheet metal as best you can
(for a good seal), and then insert the new vent seal into the old vent,
making sure that you insert the curved part of the gasket into the curved
part of the vent. Make sure that the new gasket is firmly seated in the
vent. This takes some time to work the gasket into the vent because there is
not a lot of room for your hand, but if you are patient, the whole gasket
eventually will be well seated in the vent. Snap the vent back into the
body, being sure to position the bottom of the vent in the metal first.
You shouldn't see water leaking through the vent anymore.
