That is right I just have the HU. The base Unit only has two connector in the back and the Bose HU has 4 connectors I am thinking maybe an amp what do you think?

From what I've heard, the stock base sound system (not touring) has only front speakers (no rear, no sub). Thus the stock headunit probably just has outputs for a single set of speakers (2 channels). The Bose unit you've installed has 4 channels (front and rear). You can either just connect the front channels or get a set of rear speakers and connect all four channels. In the touring models, the Bose amp splits a signal off the rear channels to send to the subwoofer.

ok that makes sense it might be the speakers and the amp that why it has to extra plugs in the back