Hardly a valid failure scenario - "Your passenger has just turned off the fuel"?
Fuel shutoff between the seats just above the floor. I seriously doubt it's never accidently been bumped off or moved. In any case, the actual purpose was for them to experience a loss of power that wasn't obviously faked. To them, for a few seconds, it was real. The typical reaction was to turn to me and perform a great impression of a goldfish. Their mouths moved, but no sound came out.