Totally Dissapointed!!!!!

What ever posessed you to run a hi-vol pump? "More is better" mentality? Chevy guy told you you need one? No matter, hi-vol pumps can cause a lot of problems. I am guessing you are on the right track with your suspicion, and it has a lot to do with your issue.

Some thoughts to ponder in no particular order:

Lighter oil drains back much quicker, try 10w30, or 10w40.

Yes, a hi-vol pump will empty a stock pan in a 1/4 mile. Run an extra quart and see if that helps the pressure loss. This will not help the consumption obviously but may help diagnose pumping the pan dry.

Oil pressure drop at high RPM is also a symptom of excessive rod bearing clearance. Since your problem seems to be a function of time at high RPM, and not RPM alone, it sounds like you are emptying the pan.

Also, based on the fact that you are obviously moving oil through the PCV system, it sounds like you are filling the valve covers and the PCV is picking it up.

A qt in 30 miles is an obscene rate of consumption. Under normal driving in traffic, what is the consumption? Does it smoke? Detonation is a real concern running under load with this kind of consumption. You can destroy things fast if this happens. Running the pump dry can also wreck things real quick.

I would strongly consider switching back to a stock oil pump. While you have the pan down, consider popping off a rod cap or two just to have a look. The top shell will show detonation damage. A plastigauge clearance check of the whole bottom end wouldn't be unreasonable either, just to see what the clearances are.