would running an aftermarket type r exhaust manifold like a 5zigen on a b16a give less gains than fitting a 5zigen b16a exhaust manifold would?
I have a jdm b16a engine in my civic with a type r exhaust manifold,decat and catback, j's racing induction kit and civic type r cams and i was told i could be losing power due to the type r 5zigen exhaust manifold and that i wold see better gains if i took the 5zigen type r one off and put a b16a 5zigen exhaust manifold on it? is this true?

 

any advice anyone?