Hello. I pulled my Onstar this week to install a Bluestar unit and use bluetooth on my cell phone. I noticed two antenna connections in the back of the Onstar. Does the Onstar have an external antenna? Better yet, does anyone have a wiring diagram to an Onstar unit? I am installing a cell amp or at least an external antenna for my cell phone to get signal when I am out in the boonies. thanks in advance.