Audi’s R8 was already fast enough to embarrass supercars costing twice as much, which did not stop German tuner MTM from unveiling a 5-liter biturbo version at Geneva in 2011 and then spending two years making it substantially wilder. By 2013 the GT version was making 802 horsepower and running to 223 mph. Read on for what MTM changed, and why the chassis work mattered more than the engine.