youngsport

hi i've got a 1998 2ltr impreza sport, when driving it periodicaly looses power and i have to pump the pedal before it will gain power again this is quite scary when pulling out from juctions as a couple of times it has just died in the middle of the road, it seems to happen when i release the pedal and then put my foot back on again though sometimes it does it when my foot is constantly on it, i've changed the fuel filter, checked air pipes, cleaned sensors, the fuel pump seems to be working ok. when the power is lost no lights come on the dash until the car comes to a complete stand still, occasionaly when i start the car the engine light stays on but i pump the pedal and it stutters and goes off.

Any ideas????