Sparky, your post contradicts itself. Extrude honing ($100 per horsepower) is the opposite of bashing in the header pipes.

Here's what I take from the video: The extra flow advantage from headers is only a small component of the total power gain. Most of the power gain comes from the pressure wave tuning.

This is the reason that shorty headers don't gain much over manifolds. Not enough length separating the pulses.

To the OP, I would say follow AndyF's examples.

Recently I have seen quite a few dyno tests with Volumetric Efficiency numbers over 100% for quite a high percentage of the operating range. It should be physically impossible for a piston to suck in more than its total swept volume. The difference is in tuning the pressure pulses, used to be called ram tuning. Isky Cams touched on it in the early '60s by talking about 5-cycle cams. The fifth cycle was overlap. I am pretty sure that at least a few of early hot rodders like Ed Winfield were playing with this back in the '40s.

R.