I bought an MT09 a few weeks ago used with a yoshimura full exhaust (has less than 300 miles on it). It sounds amazing but I noticed some brown pitting/ staining in the pipe before I purchased it. I think it might be from improper cleaning before the exhaust got mounted and the heat cycle burned some fingerprints and oil on it. Are there any ideas if this can be cleaned or polished off? Appreciate the responses in advance!