stupid bucking problem

[Sierra89]

Hi all, not sure whether my truck is a classic yet or not, but I thought i'd try posting this here. My 89 Sierra with the 305 has developled what i can best describe as a bucking problem when I'm crusing at a steady speed. As soon as let off the pedel or accelerate the bucking stops. Also, if im driving really slow, and barely toucing the gas pedel, the truck almost stalls. Any thoughts as to what might be causing this??

[ChevyTech007]

Pull your coil wire off and check for corrosion.