First off, your headers are just junk. I don’t know how many times that needs to be repeated, but that’s all they are. If you have no grasp of how overlap works, and how in a wedge headed engine how hard it is to get, and get it right, then me explaining it won’t do you any good. You have killed ANY overlap you may have had with that header, and yes you need overlap. You can claim you’ve tried real headers and that they made nothing over a set of zoomies, but I’ve tested it many more times than you, and not once, not even once was a zoomie anywhere near a correctly sized, tuned header with a collector. Until you fix that, the rest of it doesn’t matter.
As for that little scoop, in dirty air (its way too low) you don’t have near enough volume over the carb. When there is essentially no plenum over the carb, the air speed goes up through the carb, the boosters pull too much fuel and you pressurize the vents/bowls and it blows even more fuel through the boosters.
That’s an explanation of two obvious things I see. There is no argument your headers are worthless. That’s just a fact, even if you fail to recognize it. Zoomie headers are for power adders (specifically a roots blower, maybe a Pro Charger) and sometimes they work with nitrous. Other than that they are wall hangers.
