someone more familiar with Gen 3's could clarify this but from what i've seen, it seems to be a pretty common issue with the gen 3 rear garnishes? i know of several guys with gen 3 wagons and they have all had that water build up issue in the rear garnish and tailgate. i guess checking seals or for cracks would be a starting point

i once had air noises cumin from my seals once i sparyed silicone spray on all the seams then rubbed them down with a cloth them reaplied and left on try tht before buyin new stuff