hello, iv had a powerflow cat to back exhaust ,on my astra for about 5 month now, i worked away alot over the winter, well from octoberto a few weeks ago, and my back box looks like its got rust on it ? iv tried use stinless stell cleaner but still big black, spots stay on even tried useing wire wool, still no joy, iv had a look under my car and the rest is ok? dunno.. , and i look around and see loads of other cars, with stainless steel and you could see your self in them :cry: , have i fucked mine by not cleaning it every week, i never got told i had to ? or have i bumped lol?