Audi has developed an entirely new electric torque-vectoring rear differential. Audi Sport's new RS5 is also its first plug-in hybrid. Credit: Tobias Sagmeister/Audi Audi Sport's new RS5 is also its first plug-in hybrid. Credit: Tobias Sagmeister/Audi SAALFELDEN, Austria—Audi may have built a reputation for technology over the years, either pioneering or early-adopting things like all-wheel drive, direct-injection engines, and so on. But it’s also true that along the way it has earned a bit of a reputation for cars that look good inside and out but maybe aren’t the most exciting things on four wheels. Not so for the models reworked by Audi Sport, the company’s motorsports division, which now also spends its time building the company’s new Formula 1 power units . And like those latest F1 cars, its newest RS5 road car also marries together a turbocharged V6 and an electric motor. How convenient.…