help

I have a 1993 chevy half ton work truck with a 4.3 l in it and i rebuilt the motor in it. Now when i start it up the codes go off 33 and 45 and i put a new map sensor and new o2 sensor on it and it fouls out plugs. Plus when the computer starts reading off the sensors it doesn't want to go when u give it gas. Its really slugish If you can help me i would appreicaite it thanks