I had a similiar problem with a dakota that I owned several years ago. the fuel return line to the gas tank was clogged at the entrance to the tank. this created excessive fuel pressure causing the engine to run very rich (black smoke from the tail pipe). I would check the fuel pressure. if it is excessive that is probably the problem. the mass airflow sensor could be bad.(common problem). also the air filter could be dirty. there are several other possible causes. pull the trouble codes for a clue. I don't the clogged return fuel line will show a code.
