opening to a valve?, small hole to either side of the manifold. how do u blockit up Options

[surfaccing]

So I got one of the local porsche club members who knows 914 to come and look at my car and check out my motor. Now he told me the holes are a opening in the exhaust valvesand it suppose to have some tube that routes the fumes to a air cleaner so that when u get off the accelerator it helps keep the emissions on the exhaust down. But he also told me I don't need the tubes and air cleaners but I do need to block off the holes if I don't hook up the air cleaner because it is a port for the exhaust and u don't want a flame spilling out ur motor.
So I see its a threaded hole so is their some kind of screw ican just put in and forget about it? Or is their a way I can buy the proper tube that's suppose to go in their and then cap off the tube?

1976 914 2l 4cyclinder motor