The recipe is simple: Subaru installs the potent 300-bhp turbocharged 2.5-liter flat-4 in the WRX chassis, which has been fitted with strengthened axles, inverted struts, aluminum suspension arms, big Brembo brakes, a 6-speed manual gearbox and a planetary center differential that sends 65 percent of the torque rearward for lots of tail-out fun. Even in automatic mode, when the torque split varies, the STi hangs its tail out under power.