1987 Hyundai Accent Past Check Engine Light O2 Gas Cup Manifold Had Change O2

in the past I have a check engine light,O2,gas cup,manifold,:I had change O2, gas cup, spark plugs, fuel filter,I gas low in fuel, filed up in a gas station, (engine light never when of), the blazer star actin up,fund my self on the side of the rod no long after,it was like it have very low fuel,two day after i ad a fuel treatment just in case if have some water,dint help, empty the gas tank clean the injectors,change spark plugs , fuel filter,but steel doesn't help,4 weeks after we ad new clean gas star for a moment but doing all over again.lost of white smoke came out for the pipes this time, what is my problem please help me to fix it, need my blazer. (I have change the fuel pump no long ago 6 o 8 month)