It's not what you're thinking. It's your back window. Ford electronically sealed your back window to the vinyl, and that seal is notorious for breaking. Mine did the exact same thing before I replaced the top. I thought the same thing you did until I was told about the window issue. If youre lucky, and you're top is in good shape you can just replace the rear window piece. I ended up replacing the whole top since mine was white. Uh, I mean gray. LOL
C&L 80mm mass air, Mac CAI, BBK 65mm tb, Steeda ud pulleys, MGW shifter, RAM HD clutch and aluminum flywheel, 3:73 gears, 2.5" Dynomax o/r x pipe, 3" MAC cat back system w/ 3 1/2" tips, Kenny Brown(front and rear strut tower brace, caster plates, subframe connectors,extreme matrix brace,jacking rails, torque brace, lowering springs), Tokico D-Spec shocks, 03-04 Cobra(side scoops, rear bumper cover, top), 6pt roll cage, white FR500's, FMS 2000 Cobra R air dam, Steeda race wing, VIS carbon hood.