Connector identification fun!

[Barry Babcock]

Working on my '87 5kcstq.
Anybody know what this yellow 4-pin connector is for:

http://www.geocities.com/workhouse_master/underdash-001.jpg

I'm trying to get my busted cruise control working, so I've been taking 
stuff apart under the dash.
I don't like it when I come across disconnected stuff.  But it really 
bugs me when I have no clue what said disconnected stuff is supposed to 
be there for--

Thanks guys.
-Barry