1996volkswagen golf 1.4se power loss?

i have recently bought a golf 1.4 (aex;enginecode) when bought it had a oil leak which i traced to oil pressure switch it was split i replaced this there are no oil leaks any where now and the dip stick shows perfect oil level but the oil light stays on untill up to 1500rpm and there is no power what so ever to be honest you can feel the torque sometimes so i know power is there it just seems as though its being strangled though its really frustrating now please someone help me lol thank you peeps