I saw this on an old post:

"In the TT, the Bose system only has one set of L+R pre-amp inputs...

IIRC, I think my bose had a center channel up in the front vent. I remember having a fader control on the stock bose radio too. My friend at Tweeter did the install, so I don't remember what connectors the harness had. We ripped everything out, and he somehow managed to cram a tuner and an antenna booster in the console under the empeg sled.

I think there is another TT owner on the bbs, I don't remember his handle, or if he has a bose system setup like yours.

Good luck!