As far as interface adaptors go:
As far as I know.. the purple wire deal was for the pac audio, specific to the OS2-Bose adaptor. This was in order to get the interface to work on the H3. Here's the website
http://www.pac-audio.com/products/pr...ar%20Interface.
Also here is a link to the directions on their web site:
http://www.pac-audio.com/bulletins/2...ringchange.pdf
Personally I would avoid the Pac-audio adaptor. Its what I had with the D1 and it would make a loud "pop" sound when turning OnStar on and off. I currently using the adaptor by metra. Not sure onthe model number, CarToys made this change.
There are now specific H3 adaptors out there that eliminate this splicing stuff.
KodiakZ is a pro on this topic fyi. He helped me talk the installer at CarToys through alot of the glitches.