1999 Chevy Cavalier Engine sputters on hills and blows out

I have a 1999 cavalier with a 2.2 liter engine front wheel drive. Currently the engine blows out black smoke, and really goes at it on hills. It has the error code number P0171 is on the check engine light. Currently I have replaced the, bank 1 and bank 2 o2 sensor with both bosche manufactured ones. IAT sensor, the map sensor, the coolant temperature sensor which has the car running some better. But still hesitates and stumbles while driving, and of course the black smoke.