ok here is where im going to called an idiot, but if the block is warped and it is in the middle, torque the middle head nuts pretty tight first, then torque the rest as usual, what you want to do is warp the head in the middle first to get it to conform to the block, what you have is a compression leak, gases working there way from one cylinder to another because the gasket isnt holding,(warped head or block) put 5 or 10# more torque on the center bolts