the VDO gauges are not worth 2 cents if you had no oil pressure you would have the oil light on at an warm idle. New engines run hotter and often the rebuilder uses a thinner oil for brake in. The dynamic oil warning buzzer is going off then you come of the highway? that would not be unusual. I tell my customer to avoid highway driving for the first 1000 miles if possible. You need to go to a thicker oil and check the basics oil temp, coolant level, timing, fuel pressure and fuel mixture. Also make sure the lower fan speed is working on the radiator

going faster miles an hour with the radio on 
I remain 
Bob Donalds 
www.http://bostonengine.com