If it's not that door seal, or coming from the trunk or wheel well, you may want to track down where the sunroof drains are. I believe there is 4, 1 running down on each A piller, and I believe 1 on each C pillar. There is a connection usually right as the hose leaves the interior, and they can get clogged up, or even disconnected.

You'll want to double check my math on that though, because I may be wrong on that.

And I feel ya on the windshield trim. My PA is steadily shedding trim bits around the windshield too.

Water leaks are indeed are to find, my first car a Lincoln Towncar coincidentally had a leak in the same area (rear passenger - drivers side)

After driving it a couple months in the summer, I started to notice a rather nasty odor (and constant interior light fuses being blown out). While cleaning my interior, I lifted up the rear passenger floor mat and discovered some disgusting slimy white mold which was fun to clean up. (about 2-3 liters of water would accumulate in the rear footwell area as I discovered later - so you can imagine the smell of stagnant water in 30+ temps in an enclosed space)

I never discovered where the leak came from despite sitting in the back during rainstorms and when I had someone spray the car with a hose.

My solution was to rip up the carpet permanently and remove all the sound deadening materials. I replaced the sound deadening materials with some towels. After every rainstorm I would dry out the towels and take out about a liter or so of water

(I also stopped bothering to replace the interior light fuses)...sorry for rambling

p.s - the Buick's waterleak is not as bad- no odor I was just doing my semi-annual leather conditioning and noticed it

@rjolly87 - sucks about the windshield trim....seems like it is just a clip in design?? - mine is totally busted and bent out of shape, its hard to tell in the picture but its straining against the glue due to being bent out of shape- hate to have to buy a new one with the US dollar where it is right now