What size
oil restrictors are you running? Could be that you could go to a slightly smaller size and get less buildup in the valve cover. Also, are your drains clear? Make sure your rocker shafts (depending on the make) are installed "right side up" as this can also lead to excess
oil in the valve covers.
What breathers are you running for the crankcase? You need to minimize crankcase pressure to allow the
oil to drain back down. A breather at the filler tube in front as well as a rear breather may help.
You might try a cut up old valve cover to run the motor and see how much oil you are getting in the cover area. This could help you decide that a smaller restrictor will still provide adequate lubrication.
Just some thoughts,
Gary