'88 1/2 ton its got issues

[Chevyike]

i have a '88 1/2 chevy. 305tbi, auto, longtube headers, true duals, no cats and 2 mufflers. here is my problem. its got a very rough idle sometimes, and it also surges goin down the road if u are only slightly on the gas. coming down from accelerating it also has starts to idle rough. but if u click it up into neutral and hit the throttle once or twice it will start to idle normal. at wot it runs great. it will even plant u in the seat if i launch it. i just replaced the plugs (bosch platinum 1) and wires (bosch racing), the o2 sensor, and map sensor. i am also gettin 2 codes. the first is a high voltage reading at the map sensor, and the other which just came on today is lean exhaust. which is wierd because during the rough idle stage it puffs black smoke and smells rather rich. any help will be much appreciated
Mike

[Kevin45]

About $9.00 for a kit at the local "A" Parts or Zones, get a throttle body rebuild kit for starters.

Kevin