Ok so some people seem to be getting some power out of the Walbro. The only valid conclusion in this regard then is that you can't reliably expect one to do it for you if you buy it now.
I pulled the return line off my fuel rail when the car was on the dyno and at about 240rwkw the return flow had completely stopped. The AFR's had started to lean a little and we stopped the run so we didn't blow the engine.
I replaced the pump straight away.
So maybe you will get lucky, maybe not. Don't let us stop you taking a punt, just be careful.