Cylinder head manni surface sanding

[306Puggy]

Question:

Where the manis mount to the cylinder head is it necessary to sand them if you have used a steel gasket previously since they don't leave any residue behind? I was not going to but I noticed I have some 400 grit sand paper lying around so I could give them a quick blast if need be. I took some snaps of the cylinder head surface. I know it is dirty and obviously I would hit it with some brake cleaner and cloth but is it necessary to sand it?







Thanks.