92 E-150 stalls, rough idle, skips, then high idle

It stalls when idling or races at a high idle. When I really give it the gas on the road it seems to run ok, but at idle or running slow it bucks and skips or races when in gear and i have to stomp on the brakwes to slow her down. I changed plugs, wires, cap, rotor, intake motor, coolant sensor, checked and cleaned EGR (looks and acts ok), and changed pcv.
Black smoke comes out of exhaust when you step on it. I checked the vacuum lines and can't find any leaks. What else could it be?? I need help guys.

I fixed it. After replacing wires, plugs, cap, rotor, intake motor, coolant sensor, egr valve checked......
It was the "throttle positioning sensor" located on the front (bottom) of the throttle body assembly. hard to get out but worth it!! 2 phillips head screws holds it in place. @ $50.00 item.