Alright, after a bit of investigation and correcting a diagram from a Bonneville, this is the pinout for the connectors to the Bose amplifier for 2001. Probably good for 1999-2001.
But there's still a mystery wire at pin B4 that is a bare wire with a clear covering.
[EDIT: Found it in this thread: http://www.grandprixforums.net/threa...e-few-wires-do
It's listed as "drain". On the correct wiring schematic, it is shown as a shield around the line signal lines coming into the Bose amp from the head unit.]
Correct 2000-2001 PDF wiring diagram here:
https://dl.dropboxusercontent.com/u/...dioWithAmp.pdf
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