Guys, My lightning has the stock exhaust on it, which terminates with some nice stainless steel pipes, which are not finished to speak of...just the stainless. They look pretty good except inside the pipes themselves where the exhaust has caused some black residue to form. I've used wadding to get most of it off, however there's some more stubborn "caked on" residue at the bottom of the pipes. What would you guys recommend for getting this off? Scotch-Brite or some real fine steel wool followed up with metal polish?