A factory tour will show that the Aero is a mass of electronics with (I believe) four 'black boxes'. If this short always appears on the road, then it must (one would have thought) be vibration induced. I would start by checking every connector, but that's much easier said than done. The other option is to run the engine at idle and waggle the wires around in the hope that this will make it blow. A circuit diagram would really help. thinking

DaveW
'05 Red Roadster S1
'16 Yellow (Not the only) Narrow AR GDI Plus 4