Black smoke from tailpipe

I'm having a big problem. I'm going up a hill on the highway and working the truck hard and when I reach the top and release the throttle I start getting black smoke. This will happen only If you press the petal to about a quarter of travel. When you press the petal the three quarters or wot the black smoke is gone and it runs fine.Back off the throttle to quarter and black smoke. If I turn the truck off and restart it the problem goes away. If you come to a stop the idle is rough and it might die, And it may snap out of it and idle fine.
Now I have done all of the bassic testing. Lots of things are new from previos owner(ignition module.coil) I have replaced the cap rotors,wires,plugs.Good ground to computer and other ground wires.The o2 sensor,and map sensor are reacting to the change.I have ran the codes several times even when the problem was happening.All past. The computer will throw a code, checked with the tps sensor. I have good vac at idle. Checked the timming and also the advance timming of the computer. I'm at a stand still. Could repalce the computer but wanted other ideas first. Thanks for the time and replys. :biggrin:
1988 Ford Bronco ll. Standard 4x4. 2.9l v-6

Hey, bud. You need an new fuel filter

sometines when this kinda shitn happens youve somehow got oil in your carb or engine block and its burning it, so open your valve cover and check it for leaking oil