sven and decoupe...go to guys if you are afraid of CK...we collaborated on many systems. wild to mild. Myself testing and rejecting. 1 3/8 down pipes, 1 1/2, 2 inch, to either 2 1/4 or 2 1/2 downstream. All custom. I run a set of short tube headers into 2 1/4, bung at the merge to the distance...