OK, remember I asked which was muffed, my new Holley mechanical fuel pump, or the new Holley 0-15 psi liquid filled guage? The symptoms are that it shows 8 psi when I first start the car, and it drops to 1.5 PSI when the engine is warmed up.

I finally had a chance to hold the 4150 mechanical secondaries open for a few seconds while smoking the tires up to speed on the freeway on-ramp, and it ran strong and smooth up to 75 mph with an indicated 1.5 psi on the gauge. Dumb question: Could the engine even run if the pressure were really 1.5? Time for a new gauge?

Now if this were my MasterCraft ski boat's fuel injected LT-1, it would be easy to diagnose. I still feel like a dope with carburetors....

http://members.aol.com/kengibbons/auto/index.htm

If it were only for a few seconds then sure it would keep running. If you would have stayed in it and emptied the fuel bowls then you would have felt it fall on its face.

As ocs408 said as long as the bowls have fuel it will run. Are your fuel lines getting hot possibly boiling the fuel?, did you try another gauge? fuel fiter clean?
To answer your question Ive had fuel pressure drop to 0 psi under acceleration, and the car didnt even hesitate, you can burn up an engine with low fuel pressure, so i would find the problem.

Is this gauge with the little diaphragm assembly on the inner fender? If so, Bleed the pressure off on both sides and let it neutralize. I've had problems with these giving bad readings dur to pressure trapped in the diaphragm housing.

Tom