Jaime is correct. But if you don't want to make a trip to the dealer loosen the muffler shield and clamps slide the muff off, inspect for damage to the cat and muff, coat outside and inside of mating surfaces with anti-seize install muff as far onto the cat as you can then re-torque everything, in a few day check for leak. Reason for anti-seize is to prevent corrosion between parts. Remember no muff to tough.