1992 Chevrolet S-10 Exhaust Black Smoke

Here is the situation :

The black smoke came out of exhaust ONLY when reving the engine up and down, but when accelerate and hold it, there is no black smoke.

Every one says check the sensors, injectors or regulator, but I think there is an evidence it's related to an incorrect ignition timing.

My question is, does the black smoke has any relation with the timing of sparks?
I assumed it because at high engine speeds, the sparks automatically advanced.