Hi all,I too HAD this water leak problem on my 05 mustang.So i went looking for the origin of the problem instead of relying on the dealer (not having any luck finding it.I found it after removing the trim pieces from the passanger side(they just pull off)and peeling back the carpet and turning up the foam underlay to reveal the floof.right where the floor meets the side panel there is a seam that is covered with a ehite sealer of somekind.BUT if you look close you will see a spot where the sealer missed on the side panel.THATS where your water is coming from.and you can only see it leak if you open the hood and pour water down the wiper vent under the hood.It leaksthen,anyway i put silacone all around the little hole and stuffed as much IN the hole and left it to dry for a couple days (along with the carpet and foam insulation.And poured gallons of water down these vents and NO water leak.I hope this helps all of you with the water problem.