I just noticed this. It is only in the biggest pipe (the "U" pipe). It is fine brown powder....like slight rust. It is along the inner surface of the pipe....about half the length of the pipe. Will this fu** up my intake air? How can I get out of the damn pipe? This kit has never been installed and has not sat it a wet environment. Maybe I am dumb and this is something common....but none of my other pipes have this. I am thinking it is slight rust from some moisture that somehow got in the pipe. Please help me. See attached photos.