I don't think it has much to do with the
oil temp, probubly just a time frame issue. Do you have foam in the gas tank/fuel cell? If so, it could be getting picked up and clogging the fuel path. Turn the pump off and it all settles back down. Also, the voltage should be 13.5-14.0 volts, not 12. You had also mentioned a return regulator, if that is malfunctioning it could very well cause the problems you described.