So I was installing a new stereo in my car and removing an aftermarket installed by the PO. I have followed the many fader disconnection posts here (thanks guys!) but found that the PO's stereo was not connected to the OE stereo's ACC, battery, ground or illumination but it is connected to some wiring that I have no clue what it goes to.

This mystery wiring has the same harness connection to the cigarette lighter as the OE stereo connection. This wiring is original to the car but I have no clue what they tapped into.

Any help to ID what the stereo is getting the ACC signal, battery and ground (no illumination) from? Should I wire my new stereo to the OE stereo's connection and tape off the the PO's hack or just use the same cables? Any help is much appreciated!