@Vagabond That looks perfect. It only draws 6A at 12V. I can't find a dedicated fuse in the fusebox for the horn, and I don't see a relay for it anywhere, so I can only assume it is drawing power through the horn button directly. If you wired yours through there without a relay to draw power directly from the battery, I'd imagine it works just fine.
I am worried about fitting it in there though. The dimensions for that horn 85W x 90L x 60H and it is really tight under there. But if you got yours in then I guess I should be able to also.
It goes in for its breakin service next week. I'll see if the dealer is prepared to do it for me. Save me the trouble of doing it.
She fits in and uses all existing wiring and connections.
I'll get a photo for you later so you can see how it fits