A second breather never hurts if you have the spot for it (not to replace the PCV though). Also you can go to a larger PCV valve and line? If you are putting out 500 hp with a small block you must have a pretty wild cam and a speciality build on that motor? You may find that even two breathers is not enough and need to go to auxillary vacuum like the header evacuation type system. The leak down will tell a lot.