[SoTxButler]

The longer runner will produce more torque at a particular RPM depending on the length of the runner. The science of pressure waves bouncing back and forth in the runners is complicated. With the pressure wave moving at the speed of sound, figuring out the valve openings at a particular RPM and then figuring out the length of the runner to achieve the exact moment that the pressure wave bounces into an opening valve is difficult at best. If you could, you would see an improvement in performance at that RPM and a small RPM range. The effect would be like a mini supercharger, but when the RPM changes, the benefit is gone....the waves are bouncing back and forth again. If the wave is headed into the manifold when the valve opens, there will be no effect. IMO, you will probably not be able to notice any difference by adding a spacer even if you could figure out at what at RPM the pressure wave is headed into the open valve.