fuel pump woes

i put on a new fuel filter and got a repro fuel pump from an auto factors company, the pump was drawing fuel through fine, no bubbles in the fuel filter and the fuel looked clean, but the revs started jumping around like crazy and my carb started leaking fuel from a front gasket so i quickly switched it off. im going to put the old fuel pump back on for now as im guessing they gave me the wrong fuel pump...or does this mean my fuel return pipe is blocked? and also will this mean my carb is buggered? engine 1.5 gl, pierburg 1b3 carb

problem solved