I was told by an independent mechanic that the catalytic converter is damaged and it has factory warranty and I should have the dealer change it. He said however that the damage is mostly cosmetic and not functional and dealer may not want to change it. Any advice on how I can approach the dealer with this problem so that they go ahead and fix it. Also, recently the car idles kind of rough (mostly when the air conditioner is on). Any advice on how I should deal with this issue?