I just finished putting in a 408 in my 57. I have a couple of questions... First, is it possible that my plugs are fouling because of too small of exhaust? I have a 2 inch exhaust and was told by the builder that the engine needs 2 1/2 exhaust at the very least. Second, are there any differences in diameter of the rams horn headers that would help it breathe better? I have absolutely no idea about these style manifolds.