I'm starting to feel like an idiot
- maybe it is for a previously installed electrical device. I just assumed with all the vacuum lines everywhere it was some neat thing I hadn't yet read about in this forum. I'll have to look really close and see if I can find where it goes. Thing is that the car looks totally stock, like nothing extra has ever been installed anywhere.
In regards to the tail light seal suggestion - there is a couple of very small streams weeping down from there, but the main amount of water is falling from up by the driver's side trunk hinge. It must be the window seal, because the only other thing could be the trunk seal and I could find no evidence of water getting past that seal. The strage thing is the rubber around the rear window looks good, no age cracks and not too hard.
Now, about that hidden huka pipe
way too long ago for me my friend