I used to be into working on cars. If you ever wondered how and why headers improve performance, here’s a low-level tutorial.
The motivation for this is that there’s a famous graduates display case at my kids’ high school, and one of them is Doug Thorley who was the main proponent of the Tri-Y header (still made by the original Doug's Headers, or by his ex-wife's company Doug Thorley Headers) back in the early 1960’s heyday of drag racing. Of course, he fled Utah for the Inland Empire many years ago.
Prior to 1980 or so, when I used to go the drag races, the header type was always a point of discussion … so in another lifetime I knew what Thorley headers were all about, but I haven’t thought about them since.