black smoke from b16a

recently my car has been smoking alot and having really really bad gas mileage and every once in awhile it will back fire or if i have it at full throttle and it will have a lot of black smoke coming out the back... i have a 89 civic hatch with a b16a any ideas??
if this makes any diff i was having trouble having it fire on the 3 cylinder so i replaced the distributor cap (msd) sanded off the corrosion that was on the button inside the distribuor cap and noticed on the old distributor cap that the prong for the 3 cylinder was green and not copper like the other ones... then i also replaced the wires with msd wires and the pluges with boshe plat 4 it fixed the problem with the 3 cyclender not firing but now there is the smoking problem.. also my car has a msd igntion system its that silver sports compact one. any ideas of what else i could replace that could be causing the problem
thank you
tyrell

your running really rich which is causing the black smoke. pull that plug again and see if its sparking all the time with a strong spark, also check to see if theres oil or anything on the spark plug