Quote Originally Posted by Mel_0180 View Post
imageuploadedbytsikot-forums1420003754.055165.jpg
...................,,
the exhaust manifolds are cast metal (iron?).. that discoloration appears to be rust..
anyway, nothing to worry about.
these parts will probably last longer than the engine.

but if you like, you might consider painting the part with heat-resistant paint.. but as it is, it's just fine.