1987 Oldsmobile Calais Fuel injector

kindly i just want to ask about my oldsmobile calais 1987 sport body(2 doors).

i have a problem that is when i drive it make a black smoke behind it and it cant drive it in a hard ways like driving to the mountain or something like that and when i drive it for one or two hours it turned off when i remove my foot from over the power pedal .i checked the fuel pump and changes it and the map sensor also and the o2 sensor but i still have the same problem.

please can you help me to solve this problem.

thanks alot

regards