So do you want to replace the gasket? That would be the only good solution, I just hope the header flange isn't warped... that's happend to me before, but the headers were pretty cheap. Anyways, I would just buy another gasket, take the old one off, scrape off all the old gasket of the maifold side AND head side, get some of that blue gasket sealer on there and bolt it up. Or you could just leave it, how bad can the sound be?