I just had a thought. A thermostat and gauge would tell you if overheat is the problem or something else. On a different engine and surely on that one too, temperature is controlled by thermostats in each bank and a high RPM popoff valve allowing for increased flow at the higher RPMs. A malfunctioning popoff or clogs in your cooling system could be the culprit. Again, knowing if overheating is the issue helps to direct you to the culprit....would me.
