I didn't use a balance tube on the engine Ray used at Bonneville and it had no difference in plug readings. I would love to see the air/fuel ratio of each cylinder as it progressed upward in RPM. With twelve holes pointing into the sky, I doubt if your manifold would see a strong enough signal to make a difference. Besides, it could very well be a combination of things that give us this overall effect. I do believe harmonics plays a big part in all of it.
