x3 audio wiring
 

does anyone know what each of the main 16 wires for the audio system are. Its an 04 x3 non nav/non dsp with factory amp. 8 i know are for the speaker outputs to the factory amp, the rest are not as clear. I am constructing my own wiring harness for an aftermarket stereo while trying to maintain function of the factory amp. I am assuming that the other 2 sets of connections to the factory system are the aux in and steering wheel controls. if I am wrong in this please notify me thanks for the help
chris