I seriously doubt they would fit since the 99-up Cobra's have the IRS in them. Their tail pipes actually run under instead of over the rearend. Someone correct me if I'm wrong. Of course there's always the way of trying them out to see what really happens. If they're free, I say just see what happens.
Almost free, a guy will give me his stock cat back for $50, but i want to know if i can use the stuff first.. im on a super tight budget, and he is a couple hours away.