still black smoke

Is your check engine light on? If it is, it can help point you in the right direction. This symptom can be applied to many different issues. They have simple code readers that can tell you what your code is (if the light is on). If you just want to throw another part at your car to see if it fixes it, you can try replacing an oxygen sensor, but since your car has multiple Oxygen sensors, it would help to know which one would be the one malfunctioning. ie, code reader