I just found a connector IN the arm rest compartment between the seats.
It looks like a regular telephone jack... hidden behind a plastic cap.

The car has telephone controls on the steering wheel and telephone digits on the stereo.
but I've come up empty trying to figure out if I have a telephone interface in the car.
(Maybe this is the OBDC connector?)

I've also found a few cables in the trunk in the compartments behind the lights.
Looks like a DB25 parallel connector, an antenna and a connector with two LEDs.

I'd love to upgrade the sound system in the car because frankly I'm not impressed...
but I want a tight integration with the steering wheel controls and the dot matrix display of the console. There plenty of room for a full screen navigation unit in the dash where the stereo is now and there is a remote CD changer in the glove box...