Dirty and clean spark plugs?

When the engine is shutting off, sometimes fuel gets in the last cylinder or two that the fuel valves open up, but there's no spark for ignition. Were they wet with gas? Were the gaps fouled? I wouldn't worry about it. Also check the contact points inside the distributer cap to make sure the contacts aren't burnt or greenish. Maybe those cylinders aren't getting a healthy spark. You should worry if you're blowing smoke or raw fuel out the exhaust. This would indicate that the piston rings are worn or your cylinders are scorched.