This drop-in replacement fuel pump from Walbro supplies up to 255 liters per hour of fuel flow. It's a must if you go with a larger turbocharger. It's made in the U.S.A., and we can tell you these things are nearly bullet-proof. (Well, not LITERALLY bullet-proof. But you get the idea.)
The included installation kit includes a fuel sock (filter), wiring harness, rubber adapter thing, and even a couple of new clamps. Note that on some late-model Subarus you will NOT be able to use the provided sock, and will have to use the original one that's in the car.
Installation is straightforward, but since you're dealing with the fuel tank and potentially explosive vapors, we highly recommend you have it installed by a professional mechanic.