Norm mentioned the intake gasket, not a head gasket. Depending on what intake gaskets were used, you could be getting a little leakage from the water passage in the intake into the intake port. But you said it seems more like fuel so I am hoping the plugs will fix it. Check the distributor cap and rotor real good too, sometimes they crack or get corroded after some run time. Again you can swap an injector from one cylinder to another to see if the problem travels to that cylinder. Good Luck and keep us posted.