needing help with rough running 350

OK guys heres the deal,I have a 1994 GMC yukon(350 fuel ing.) it would miss every so often on idle,like a spark plug wire jumping,(has new wires) I replaced plugs ,#4 was real carboned up,the rest were some what black and a little wet,I replaced with the boush platinum,ran real good for a week,now when I stop then try to go,it misses really bad , like plug wires jumping or floating out, so I checked plugs, they were all wet and had black carbon on them, My question is what do I look for ? is there sensors or something that controls the fuel on this ? I don't know much if anything that have computers,:confused: I really would appreciate some help or feed back. thanks...::confused:

In addition to what Denny has said, why not try a bottle of injector cleaner?

thanks guys ! took Dennys' advice and went to advance auto,
they run a test on it, they said it was the oxygen sensor, (pricey little thing ) but hey!! it works.......

With fuel injection, two times out of three, its the oxygen sensor.