Maximum output at 75psi is fine, and leakdown at 65psi after 10 minutes is fine. The only other thing is volume, should be ~ 1 quart in 30 seconds, I don't think you'll find a problem with that as the other numbers a good.

Now you know exactly what the pump is supplying to the injector and the fuel pressure regulator. Checking pressure and leakdown at the service port will indicate what regulated pressure is, (when the pump is running). It should be 55psi to 61psi. If it drops below 50psi at the 10 minute mark, you know the leak is either in the pressure line from the fuel filter connection to the injector, the injector itself, a spider line, a poppet valve, the regulator diaphragm, or the valve plate in the regulator. To check this stuff, the plenum must come off and the poppets removed, then pressurize the system. If there are no visible leaks, check the regulator valve plate. To determine if the valve plate is leaking, (internal leak, not visible) the system needs to be pressurized. Immediately after the pump shuts off, seal off the return fuel flow to the tank, (gotta do the "creative plumbing" thing again). If pressure holds, the valve plate is leaking. IMPORTANT: Do not restrict the return fuel line when the pump is running. The regulator diaphragm can/will rupture if pressure at the service port exceeds ~75psi. Keep in mind that the leakdown test does not test for leaks that are downstream of the regulator valve plate.



The arrow on the left is the fuel inlet from the injector, the arrow on top is the return line going back to the fuel tank. The vacuum connection is exposed to manifold absolute pressure inside the plenum so no vacuum line is required. Pressure is regulated by a combination of manifold vacuum and spring pressure on the diaphragm. Low vacuum=high fuel pressure, high vacuum=low fuel pressure. The highest possible fuel pressure is achieved when the engine is off, (zero vacuum) that's why it's checked with the engine off.

 

No O rings, the poppet nozzles just snap into the manifold.

What is the regulated pressure with the engine off and the pump running? GM does not publish any "engine running" pressure specs, there are far too many variables involved.

Leakdown to 33psi is a problem, there's a leak...somewhere, not very big, but there is a leak. Activate the pump with the plenum removed, and the poppets removed you might see a leak If not, check the regulator valve plate described above.