ranger2nd75th

i am looking for some serious help. i have a 1996 legacy outback 2.2 litre 4 cylinder. the engine keeps cutting out as if one would think it might be the fuel pump. i have replaced the fuel pump, fuel filter, fuel hoses, spark plugs and wires, sprayed the mass air sensor and checked the vacume hoses. cannot find a vacume leak. fuel flows fine. car ran fine for the last month and the problem re-acured this morning. so now i am at a loss. if i let the car sit for an hour it will start fine but when i put it in gear and give it gas it spudders and cuts out........ any one have any ideas what i am dealing with

i am looking for someone to help me figure out an engine miss problem. the engine cuts out like a fuel problem. starts to spudder then cuts. if i let it sit for and hour it will start fine but when i put it in gear and give it gas it will go for a good 30 yards and start to cut out again. all fuel components are replaced. spark plugs and wires. spark unit still good. new battery and cables. dad thinks it might be a vacume or o2 sensor problem but i am not too familiar with either.