Need help finding a switched 12v source for turn-on lead. 2013 Audi A4

As the title says, I'm installing a basic add-on amp/sub to a '13 Audi A4 with the B&O system. I'm having a hell of a time finding an ignition-switched lead in the rear of the car to trigger the amp turn-on.

I previously did the same basic system in our own 2010 S5 and found a switched lead in the fuse panel on the rear passenger side. But on this A4, the entire fuse panel is hot/live all the time.

Any help would be appreciated.

Thank you!

Turborusty

There is a black wire in a harness behind the fuse box that is ignition.

https://farm1.staticflickr.com/886/4...e4027fbc54.jpg

Is this the fuse box behind the passenger side rear panel in the trunk?

No, it's the driver side front by the kick panel.

Ok thank you. Looks i'm running a wire up front. I appreciate your help!!