The STI uses Subaru's Multi-Mode Driver Controlled Center Differential (DCCD) version of the Symmetrical All-Wheel Drive system. Using a planetary-type center differential -- which is somehow augmented by a mechanical limited-slip type center -- the STI defaults to a rear-biased 41:59 torque split.
After being split fore-to-aft by the center differentials, the torque is again split port-to-starboard by a helical-type limited-slip front differential and a Torsen torque-sensing limited-slip rear differential. I'm counting at least three types of differentials in this MMDCCD system.
In the cabin, you'll find black and red trim centered around a new flat-bottom, leather-wrapped steering wheel. Just beyond the wheel, the driver monitors the vehicle's systems with a new 3.5-inch LCD screen in the center of the instrument cluster.