paul: the pump only pumps what the ecu tells it
the main advantage of earthing the pump and causing it to pump at it's max speed, is that it helps with stalling
but also when changing gears the afm sends a signal to the ecu, saying it's not being told to suck air in (not boosting - changing gears), so the ecu tells the pump to slow down, but then when you get back onto the accelerator the pump has to flick back up to full speed ... you therefore get a large amount of fiddling and a 'step-up' feel from the pump (minor loss of power)
with the pump engaged at full all the time, the fuel is still being pushed through ready to ignite with the changing air, and not being tripped about by the ecu
sorry if this isn't making any sense (even though I'm english, I can't seem to express things properly )