FINALLY a test that makes sense! It is indeed fuel starved. I didn't catch it before because pressure starts high and slowly declines under sustained throttle. I made a 3 minute video with the fuel gauge attached showing the problem:
https://youtu.be/D8EWqHjmkqA
I guess the next step is to remove the fuel tank and check the sock. Thank you for the suggestion! This rocks. I feel like I finally understand what is going on now for the first time.