After four visits under the headliner, I finally cured my rattling, vibrating noises.
Through this process, I got really fast at disassembling the interior of my car, but I hope to not need this skill in the future.
What I found to be rattling and vibrating was above me, at about 4:00 relative to my position in the driver's seat. I could make the vibrating stop by pressing up on the headliner, so I knew that this was where I needed to look.
On a previous visit under the headliner, I had secured the clips that hold the headliner up by adding double-sided foam tape to the tab that protrudes from the clip, sandwiching the tab so that the clip couldn't move in its holder. I also put duct tape over the clip to isolate it from the metal of the body.
Unfortunately, that wasn't the source of the rattle.
I also duct taped down the wire that is visible when you pull the headliner down.
Refer to the images in
schrute's album
Unfortunately, that wasn't the culprit either.
Having pinpointed where the noises were coming from, I slid my hand further under the headliner towards the front of the car where the inside of the roof curves upward. Just ahead of this curve, I found another wiring bundle coming out of the satellite/navigation antenna. I wedged foam insulation under this plastic covered wiring bundle and taped it securely to prevent movement.
I can't show you a picture of this because there is no way to get the camera in there. Just slide your hand in there and you'll find it just to the right of the antenna!
While I was under the headliner (again), I re-insulated the wire closer to the hatch, securing the plastic clips with double-sided foam tape, wedging foam insulation between the wire and the metal roof, and duct taping the whole thing down.
I can proudly say that my car no longer rattles over bumps, no longer vibrates to the beat like a $500 hooptie with a $5000 stereo, and most importantly, I can drive down the road without constantly looking up at the headliner.
Hope this info helps those of you who have rattles over your heads!