what header are you using and what motor was it for? KJ (from this board) and I were talking about a friend of mine who was having the same problem. KJ was telling me the b16a manifold is just a tad bit shorter and therefore is too close and just barely touches the pan and causes the gasket at that place to fail. So if youre running a b16a manifold or header look at the clearance and the place where the leak is occuring and if it appears thats the problem switch to a b18 header.