auditorium completely dead.

Not sure with the radio, the display dims when the lights are on, I know thats obvious but all I can think of.

The button could be a retrofitted sprint booster? (if you don't know its a popular mod on this car to increase throttle response). You could check that by driving it and flicking the switch, if it is a better response then its probably what it is.

if not your going to have to trace the wire back.
 
When I had my car a week this happened to the radio and I pulled it out and the multi plugs at yhe back were loose (quick fix) also check your fuses mate :wink:
 
Also now noticed that the steering wheel buttons for CC and speed limiting don't work either. Starting to think I have bought a bit of a dud