1990 Mercury Cougar that is bucking and sputtering.

I have a 1990 Mercury Cougar 3.8 NA that is bucking and coughing at all speed and has a very rough idle only while in drive with black smoke coming out the exhaust. It has new head gaskets, water pump, alternator, and other misc. I need to figure out what is wrong cause im stuck at my sisters house and need to get home.