I have removed my CAT to replace it with a High Flow CAT and I drove it around the block without it on and I would not suggest removing it. It was so loud that a cop has sent to my house to tell me to turn off my car and fix it. If you have ever been to the track, its about as loud as that. As far as the blackening goes I would look at drilling outlet holes before the muffler just to reduce the temp at the end.