Odd fuel/throttle issue

[KMW-NWXJ]

Well, I have bypassed the fuel pump relay and the resistor with no change.

I have verified that the system is working as designed, i.e. fuel pump runs about 2 seconds when key is turned on and then stops, shut down by the Auto Shutdown Relay, as I understand it. Then when you start cranking it over the fuel pump starts up again, powered through the starter circuit, according to my research. Then once it starts, the fuel pump is still running, now powered through the fuel pump relay circuit, per my research. The pump sounds smooth and normal at all times.

I went and rented a fuel pressure tester. Per my research pressure should be 30-40 psi, and should pressure up and hold from the initial 2 second priming when the key turns on. Idle should be about 31, and with the vacuum disconnected from the regulator it should jump to 39.

I hooked it up and on prime it jumps right up to 40 and then instantly settles at 31. Once started it idles at 31 and jumps to 39 with the vacuum off. Seems to be as it should be. However, it still fell flat when you try to give it throttle, and still needed full throttle to start and would sputter and cough several seconds before it could idle. Once shut off pressure held at 31.

Now here's where it gets weird. While it was running I pushed the pressure bleeder for the tester just to see the fuel flowing. No real thought or reason, I just did. I let fuel run out the bleeder line for several seconds. Then I hit the throttle and it revved smooth and normal! Shut it off and it started right back up normal with no throttle and again revs fine.

Now I'm really stumped! It's running just fine and I can't get it to sputter, and nothing has changed! Is it possible there was a vapor lock issue in the fuel rail? Or some kind of debris that was blocking an injector that got flushed out when I let it flow through the bleeder line? That's all I can think of at this point. I'm at a total loss, and I feel like I just can't trust it!

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