Not true. I tested that. In a 3 gallon cell.
Every railbird that saw it told me how stupid I was.
So I spent an assload of money to put the fuel in below fuel level. It did zero.
Unless the tank is almost out of fuel it won’t make any difference.
And that was with MFI, which sends more fuel to the tank as rpm goes up. With an electric pump it returns less fuel as rpm (and power) goes up.