kooks headers?
It's not so much that the 1-3/4 stepped to 1-7/8 offer the flow of the larger primaries but the smaller diameter primary first helps with velocity and pulls the exhaust out of the head. There have been instances where they have been proven to make more power than 1-7/8 but I haven't seen any done on an fbody and also they are much more$$
mine are not coated though it looks much better imo.









