Hey mate,
Do you mind linking direct to the TSB you mention? I want to compare notes and see if my solution is similar/same.
The dealers here in Australia are pretty sloppy when it comes to TSBs.
You mention excess sealant in the HVAC unit. I'm very curious because for me it would've been lack of sealant/adhesive that was causing my rattle. I posted a massive log of what i've attempted to do to fix it here:
Dash Board rattle
In summary, for me it was a hollow rattling/tapping which occurred only within 10-15mins of a cold start. Sounded like something stiff rattling on a hollow plastic object. It sometimes occurred on coarse road. The noise sounded like it was coming from under the dash, in the barely accessible regions. I've thumped and pressed on everything to no avail.
Solution: Tape down the HVAC aspirator joint (the part which sticks out of the HVAC unit and connected to a 15mm rubber pipe with a U bend, which goes to the cabin temp sensor by your knee. Without the tape, it's very easy to jiggle and replicate the noise by hand. I've used 3M electrical tape for now but might find some heat resistant tape as a long term solution due to proximity to heater pipes. Maybe kapton tape?
It looks like there's a hole for a self tapping screw to hold it down but doesnt look like there ever was a screw.
While you're there, wedge some black neoprene between the U bend in that hose and the carpet to eliminate any possible wobbling of the aspirator.
Pic will follow shortly when i get home.