I can't think of how high or low pressure would affect your fuel. But, those mechanical problems can certainly affect performance. As soon as the bearings get scuffed, the moving parts will not move as easily and may generate more heat. And when the bearings seize from oil starvation, there will be no performance at all. High oil pressure can blow out or crack brittle gaskets causing oil leaks, and can even blow out oil filters. Low oil pressure can starve bearings in the engine of lubrication and proper cooling. For normal driving, you really want to keep your oil pressure in the "happy" zone between 40-60 psi. Some racers who run at higher rpms want higher pressures for extra cooling and protection.