I have an Intruder Lc 250, 2005 model. On purchase, it has corrosive like marks on the exhaust pipe. The previous owner tells me that it occured by having someone wearing runners with their foot on the pipe. It has a kind of petrol splash effect , pock marked. Kind of light a rainbow imprint with oxidization marks, which they apparently have had no luck in removing with a clean and buff. Any ideas on ways to remove this residue or how likely this is the cause of it?