If it's the rockers, you can clean them out with a piece of wire and some penetrating oil. The rocker shaft is hollow and has holes where the oil feeds into the rockers, and it goes through channels and drips out onto the valves and pushrods. Then say a little prayer that it's that and not the cam. If it does turn out to be the cam, a cam change is one of the best ways to wake up the six. The other biggies are cylinder head work, exhaust and intake.
