The Impreza has wiring for its own system (very cheap to buy now in a kit, as SubeTek said) and the plugs are not the same as you already know, except maybe for the dashboard switch. The controller uses a single white plug (16 or 20 pins, can't remember off-hand) and in the engine compartment there's a 4-wire plug for actuator, taped to the harness near AC lines at the bulkhead.
That plug is all you have to work with. You'd need to look at a Legacy wiring diagram to see if the plug can be used to run a Legacy pump and actuator. I have a '95 Impreza diagram, in case it might help. The two things you're asking about are probably relays, or relay sockets, although I haven't seen a control module from a Legacy. They aren't used on the Impreza.