I bought a set of Kooks headers for my Chevy SS which came with gaskets, both gaskets burst quickly. After talking to some of my mechanic friends, I quickly found that the stock GM LS3 seals are much more durable. Live and learn, a lot of work to replace them, but no problem. I might add that I have a supercharger under the hood, so the exhaust gases are definitely coming out of the cylinder heads hot. Thank you GM!