check the codes
if its stil the o2 sensor then it might not have power to it
but u said it runs better now with new sensor so might be a new error code in the ecu
disconnect the battery for 30 secs, this erases any old codes in the ecu, then road test and when the light comes on again check the codes
post me what codes it flashes if u dont know them and i can try to tell u how to fix them