Try a different valve cover that has baffles. Sometimes the breather/PCV opening in the valve cover is in a bad spot and gets a lot of oil from the rocker arms. The baffles will limit the amount of oil that travels directly into the PCV. You don't want to completely eliminate the system as you need to have some sort of crankcase evacuation system. You could also run a crankcase evac system with breathers on both valve covers with hoses piped to your exhaust. No oil to go into the intake manifold carbon up the plugs. The plugs stay cleaner and the extra gases go out with the exhaust. Not good if you have to pass emissions testing.