Damn header leaks! wtd?
you NEVER said which headers youn are using i have a set of doug thorly try Y (with3/8 flanges) my gaskets are HIGH TEMP RED SILICONE ONLY put it on header bolt up with locking bolts let dry for a couple hrs b4 firing and ive NEVER had a blowout if that dont work for you use Mr gaskets with a good coating of "copper coat"" that worked on my /6 with a 6into one direct connection header good luck