A VISITOR FROM STUTTGART FOR THE DBX this month in the shape of the Cayenne Turbo GT, the super-SUV that Porsche sent to its Weissach GT department for a workout in order to show the Brit upstart who produces the best performance SUV. It’s a sector that remains a mystery to many of us, in terms of why manufacturers invest so much to chase performance figures with cars you would never start the process with in the first place. But bills need to be paid, investors rewarded with dividends,
