I have a 2001 cobra. It used to make a little bit of a rattle when it was cold. It would only do it under part throttle and would go away if you gave it more gas. When it warmed up the noise would stop. Now it starts at part throttle and continues all the way to wot. It doesn't go away when its warmed up now either. It's been running a little lean. Now bank 2 is really lean and that's the side the noise is coming from.