99Tahoe(OldStyle)Brake Controller Wiring

[KeithsTahoe]

I am in the process of wiring the brake controller. The vehicle has the factory towing package. I used a T-connector to plug to the 7-pin connector. I know where the brake connection is made in the Convenince electrical panel for Stop Lamp Switch. My problems are as follows. I do not know where the two extra wires at the rear(where the T-Connector was installed) are coming from up front. I am trying to figure this out so I can use one for the brake line from the brake controller to the rear 7-pin connector for the trailer brakes. I do not see the two wires up front. They must be hidden or under or behind something. Any help would be greatly appreciated.