If this is a "new" setup this season it is a good chance it is vapor lock. I have external dual pump and really gey loud and whine after a half hour of running. The fuel temp seams ok with little change and amperage draws stays same they just get loud. They are dual 320 pump size. Your in tank pumps will be putting heat into fuel. I insulated my fuel rails and added larger 12 an line to pump suction in hope pumps run cooler.