Yep I bought and used a new gasket because I never reuse exhaust gaskets. But the design of the gasket makes it ok to reuse the old one when I installed the new one. I had to be carefull not to mix it up w/ the old one it looked just as good. I kept the old one to reuse with the stock exhaust manifold aswell.
I've had my xB since a month from when it was initally released. With that being said, I've had to wait for mods to be released, and then R&D them myself. I installed my header when I had appx 15k miles on my xB, and I reused the the gasket. I haven't had any problems and that was almost 3 years ago.
I suggest reusing the gaskets. They are quite durable and unless you drop them or bend them in half you should have no issues. Once you put on the headers, if you have leaks, check to make sure everything is tight and the gasket is sitting in the correct position. If you still have leaks, then change your gasket. I would be suprised if you have any problems with it though. Good luck!
thanks for all the help guys! Ill hopefully get my header soon, prob have to wait a few weeks before I put it on but Ill go ahead a reuse the gaskets. I have my Fujita SR in my room, hopefully put that on this weekend.