It's supposed to run under pressure. That's engineered into the system because it raises the boiling point of the coolant when it is under pressure.
You say borderline oveheat. That's pretty normal too. The cooling fans on most of these vehicles aren't even programmed to come on before about 225deg. Watch you gauge and the cooling fan. If the fan comes on before the temp reaches the red and the temp immediatly starts coming down and comes down enough for the fan to shut off, the car is normal.