I was in the process of installing a new stereo that requires a
switched power source.  After searching the archives extensively and
reading all the suggestions I decided to post my solution so others can
benefit.
Not wanting to splice into any wires or have the stereo on with just
the key in the ignition I located an empty terminal on the fuse block.
Relay block 7 / terminal 2 will provide 12V when the key is inserted
and turned to the on position.  After review the Bentley it appears
this block is empty on years 86-91 but I can't be for certain.  It
definitely works on my '88.
Just wanted to get this in archives for anyone in the future.

Barrett
'88 Wolfsburg