98 k1500 305. Started to have a slight bounce in idle a few weeks ago. Took it to get beer n smokes other nite n would barely run. Almost died at stop light. Gets up around cruisin idle its not as noticeable. Had a full tune up this spring with plugs wires cap rotor n filter. Previous owner did new pump before I bought it. Fire it up n it fights to idle and bounces from 200 to 900 rpm in park or in gear. I'm planning to LS swap it in spring but would like to have it driveable incase get a bad snow over winter. Any ideas where I should start looking?