Improved exhaust flow with headers is a myth- - - - -UNLESS you go with a very expensive custom designed setup with equal length tubes from every exhaust port, and the tube length will only benefit performance at one specific RPM range. Generally, the longer the tube, the better the low-end torque will be. A tractor pull engine I built with a Dodge 440 needed header tubes 8 feet long to get the best pull off the line, going into a 6" diameter collector. 30-something years of dyno run documentation of that, accumulated by my father and I, got destroyed when an assistant principal at the high school where we both taught decided to discard a filing cabinet full of old shop records. He didn't like my opinion of his ancestry after that episode, which included references to a bunch of dogs and frogs!
Jerry
