My drag car has stepped up primaries, then merge collectors. I haven't seen much of that on motorcycle pipes. I like the unpolished stainless pipes too they have a cool grey color.
I know a header speed secret but if it got out I talked, someone (not me) could lose his job. Probably wouldn't apply to our stuff, high end race only deal. Someday when it's not top secret, I'm going to try it.