Look at left hand carb and the round 2 bolt cover on its' outside, there's a rubber valve under it that soaking will ruin and one on each carb. Those valves are pretty expensive.
Depends on whether the throttle shafts are stuck or the actual butterflies in bore, the latter are extremely sensitive to clearance and any corrosion at all may have carb where it cannot idle as only thousandths of an inch opening there, corrosion will wreck that.
Requires breaking the carb bank apart to see which one(s) is messed up and that makes you remove at least one choke plate off each shaft to get them apart to get to the valves too. Choke plates are staked and the stake points need grinding off or else it ruins the choke shafts there.
