Tony, you are trying to catch me out.
The issue I covered was your suggestion that the Subaru figures are incorrect. The figures obviously are meant to apply to a pump free of any head.
If the flow rate increases against a constant head, as a result of increased RPM, there will not be an increase in pressure, unless the head is increased, or a restriction is introduced. Therefore any restriction has a direct relationship with pressure.
You are saying that if the flow rate is increased (as a result of increased RPM), the head/restriction becomes more relevant, i.e. a bigger issue. This can be construed but it has nothing to do with the original subject, which was pump specification.
You were stating that the Subaru figures covering the pump are wrong. Their figures will not refer to the pump operating against a head, i.e. as per the Reliance Electric graph 1, which in fact proves my original point.
Graph 2 covers pressure and does in a way, relate to your suggestion regarding the importance of any restriction. However the graph shows this is may very well be less than you had reasoned. The slight curve shows that pressure increases at a rate dependent on speed, presumably with a constant head creating the pressure.
The pump curve you have shown, covers flow rate as against a variable head together with power consumption and has no real significance, unless one loosely relates power to pressure.
Back to square one, left head overheating, due to a restricted junction. The restriction is shown to be of less importance at high RPM, due to steep angle of graph 2. No problems at intermediate RPM. Why is not a small degree of restriction in the right leg, a valid remedy?