I would check to see if the draft tube is restricted. It is designed to have fumes sucked out of the crankcase at higher speeds. The air supply to replace this action is replenished through the slots in the valve cover or a vented fill cap. Any condensation in the system will likely move to the highest point in the engine (the valve cover). If you don't have good flow through the draft tube, the condensation will not be completely purged. I would also suggest that you pull your spark plugs and see if any of them are much cleaner than the rest of them which would indicate a cracked head or bad head gasket (small coolant leak with steam clean the plug).
