Like said above......2 1/4".
Not sure if you still have the stock mufflers, but this would be an ideal time to upgrade the catback if you haven't already. Most catbacks are 2 1/2", but some have 3" or 3 1/2" tips. Flowmaster probably has the 2 1/4" catback kit, but I'd bet they have a 2 1/2" catback for our cars too.
Also, if the scratches aren't too bad, you could wet sand them by hand (use very very fine sandpaper that is very wet). I did this on the stock tails and they came out really nice.