I would probably start at the begginging of the headers and work your way back with new gaskets. Ive seen people recommend Grimmspeed gaskets. Siruda gaskets came with my headers and had a nice crush ring in the center. I would recommend using Accosti Seal and every gasket,flange, seal ect. Here is my thread on header install you can see where I put the accousti seal.
http://www.ft86club.com/forums/showthread.php?t=119961