I've found all sorts of aftermarket exhaust flap controllers for the W213 and W205 versions of the M276 Turbo engine, but am not sure if they would be compatible with the W212. Upon startup, with the flaps/valves open , the car sounds quite mean, but it quiet downs to a whisper within 45-60 seconds. I'd like to be able to invoke that sound on demand, and was curious if anyone had found a solution. Unfortunately , there were so few of these cars sold, most after market companies don't even know they exist.