I thought it could be the rear defroster relay but those colors don't match up. It might be the connector for the cruise control stalk, but it's hard to tell until you give more details.
I wondered the same thing on my 85, I seen it a few days ago..
Yeah, like just about every car I'm pretty sure they made one wiring harness and used it for all the V6 Automatics no matter the options and one for manuals/4cylman/4cylauto or just one that covered all possibilities. So you end up with wiring that may not be used because an option was not installed. Like my Neon out in the garage. I swapped bumper covers to a model that had fog lights from one that didn't. All the wiring was there for the fog lights, all I had to do was plug them in at the bumper, get the dash switch from the junkyard and put in a fuse.
[This message has been edited by Khw (edited 11-08-2013).]
You are exactly right, the wireing harness is set up for all options no matter what your car got when it left the factory. That's why adding in options is basically plug and play for the most part.