Scia

Car is throwing grey smoke, bought the car w/ a chopped harness & p2p ecu. Hence the ecu is in limp mode w/ o2 sensors also throwing codes. Would that cause the car to be all F'd up. Would anyone recommend buying the p28 / harness and hope that it solves the problem. Dont want to put 300+ into something that will not completely solve my problem. I check the oil weekly, and dont see any loss; radiator fluid is also checked w/ no sign of fluid loss. Car is a 92hatch d16z6. Any feedback?