I've just been hearing about the hardest working Porsche 911 Turbo in the world: the one that Nissan has been using to benchmark the new GT-R against. 
Apparently the Turbo (a current generation model) has covered over 30,000 miles shadowing various GT-R prototypes at testing sessions around the globe, including hundreds of laps at the Nordschlieffe. It's even got its own dedicated mechanics to keep it in tip-top condition - Nissan doesn't want Porsche to be able to send a 'fresher' Turbo out at the Nurburgring to retake the GT-R's hard won lap record.
Of course, that also means that Nissan has spent tens of thousands of pounds on genuine Porsche parts including dozens of sets of brake discs and pads.
More amusing, from the point of view of Nissan's development team at least, is the fact the 911's full telemetry kit and roof antenna made it irresistable to spy photographers, with shots of an alleged Porsche prototype turning up all over the place.
The big question now is that of whether Porsche is too proud to reverse-engineer a GT-R with the same brutal efficiency. Don't be surprised if Walter Rohrl is dispatched to the Eiffel Mountains in short order, and in a new GT2, to try and reclaim the record for Weissach, a well-used, grey-imported GT-R trailing in his wake.