Do you know what this is??

[bmxmon]

Hey everybody, I am having trouble trying to figure out what exactly this is. I will put some pics of it up so you can see it. I brought these pictures to Napa, and they couldnt tell me what it was for! This hole seems to connect all the exhaust ports through, from what i believe is those EGR ports. Any help would be awesome, i need to know where i can get a new one. Pic one is of the side of the head where the block off thing is missing, the other pic is of the one that is still there. Thanks.