Originally Posted by hammertime

Windage, or oil splashing into the crank at high engine speeds, is the probem. If the oil level is that high, it can cause aeration or foaming that would lower the oil pressure (air is compressible, oil is not) and could eventually damage the internals if uncorrected. Lowering the oil level should not lower the pressure, unless the remaining oil volume got hot enough to change the measured pressure. Lowering the oil level should only prevent oil from being that high in the pan under higher rpms.

The real question is, how much oil is in the top-end when you are driving? I've heard the LS1 traps a lot of oil in the heads before it drains back, and that is one reason for oil consumption on cars with stock PCV that are not vented from the valley cover.