In Subarus, cars with automatics have a 90/10 torque split while cruising to offset the dragging of the rear wheels (electronically controlled transmission control unit), but the manual models have a 50/50 (Center differential with a viscous coupling device).
Subaru's All Wheel Drive System - AutoWorld.Com
I was actually thinking about looking for an Impreza for my next project, since there's so many more aftermarket parts out there than there are for Tempos.