Hey Jake,

Just an observation but those primary's look pretty big. I am not a header designer nor do I claim to be one so please just hear me out. I realize that the primaries are probably the same size as the exhaust port but I have a theory that by doing this we are suffering from "More's Law". After seeing 240's VRP headers losing torque and only gaining 8 HP I started to think about the size of the primaries as being the culprit here as I have never heard of a piston driven engine that couldn't gain from an efficient header(s) setup.

See in my CAD-like attempt at a primary tube with a contoured step down to increase the exhaust velocity. I was checking out the long tube headers that EVOSport built for the 6.2l V8 and you can see this being used too (highlighted in red). I'm not saying that is why these headers made so much power because they are afterall long tube headers with Burns Stainless merge collectors, but I'm sure it did help in keeping that exhaust haulin' *** through those tubes.

Another benefit of using smaller primaries is that there would be a bit more room to snake those tubes around, not much especially on these R170 chassises but I'm sure it could help.