Under the valve covers on my motor, there are "PCV" style components. One for each head. Allows venting of crankcase. These are not in the intake manifold. Depending on year, the 305 had draft tube and filtered breather can, PCV/air cleaner combo. Valve cover breathers......... don't know what you are talking about or asking for sure. It's nice when someone gives the year and the motor size when posting. I don't see any answers to a question you had. But I don't know what the question is? Fuel economy? Detonation reduction? Lean condition problems? Are you talking about the Ebay motor I got you? You are welcome.