/6 headers

For the record, it is my belief that the improvements in performance of your design can be largely credited to the increase volume of the "collector". If I was a pulse of exhaust, I would think a standard design, with a smooth merging into the collector, would offer less resistance. My belief is your system offers benefits, because of the dropoff, from a small primary to larger "collector" and that once, the "collector" is pressurized, it will start to flow out the exit of the "header".

I believe that the added volume of your unit is an improvement over the stock manifold, since it has 2x as many exit points, and it is not 6 into 1. I believe that it could be bettered with a long tube standard header, and I believe the best compromise would be a shorty, or 3/4 standard tube header, with quantity 2 of 3 into 1 collectors, to offer the best for flow and fit.