I'm pretty sure that is is something in the column and not just a loose cover.
Still trying to work with the dealer, and they have been pretty generous so far in sending their junior mechanic on road tests to try to diagnose the cause of the noise, but the mechanic seems to think such column noises are normal .
I also have a 94 LS400 with 180,000 miles, and it's column is solid and quiet.
I'm trying to find a schematic of the 2003 LS 430 steering column assembly, if anyone has one...