When I think of the words "engine manifold" I think of these.
I saw this tweet by Elon Musk which shows the image below, and then there is a reply image with a checkerboard pattern behind part of the manifold.
Question: What are we looking at? Is this cooling metal, or is it still in the mold? What is that checkerboard pattern in the 2nd image? What part of the engine is this; what items does it connect?