holes in manifold?! input appreciated

[joeltoyota]

I recently replaced the gaskets for the exhaust manifold on a 20R 4-cylinder engine on my 82 toyota pick-up. I didnt put the cover back on when i re-assemble it because it wasnt worth it but the manifold has two holes on the top of it where some of the exhaust comes out. Now, before the cover would have normally directed that exhuast back into the air intake for pre-heated air im assuming. I need to know if it is necessary, or if i can simply cover up the holes on the manifold even if its just temporary because when they are wide open without the cover on them the engine is incredibly loud and doesnt seem to run as well.

any thoughts on this would be very very very appreciated as i have asked around quite a bit.

[69GTO]

tap em and block them that is what I did on mine