I just pulled the intake manifold off of my Hardin Marine 5.7L and noticed the new intake manifold gasket set I have doesn't have the rear intake passage block plates that the motor came with. The little rectangular shaped tin piece that covers the last rear ports. Do I need them? I was thinking that they were probably there to help warm the engine? I do run a thermostat. And being this is a jet boat, I also have a gate valve limiting the water flow to the motor. Do I need them?