The system pressure should set to a number 1/2 to 1 psi lower than what the system can maintain for your power level(unless it will maintain more than enough pressure, then set it to where you want).
You’re not understanding what I’m saying.
Let’s say you turn up the regulator to 15psi, and retest with the valve to set to maintain 9psi, and it still takes 115 seconds to pump a gallon.
Then, in operation ....... you set the pressure to 9psi....... and the pressure drops as soon as the motor starts making over about 375hp...... and the floats drop.