I would suggest that before the oil pressure valve is adjusted/ replaced that the oil press.gauge and transmitter are check calibrated,and the filter is checked/replaced as well...You may also want to check it is using the correct grade of oil...especially after overhaul....It is important that you do not use any significant power until the oil temp. is up to 40 deg C,no matter what the OAT is....Remember,the mechanic doesn`t usually fly.......