The slight pressure imbalance side to side is probably due to the tyres on one side being sat in direct sunlight for a time and the tyres on the other in shade. Recommended tyre pressure settings are for tyres when cold iirc [Tires are considered cold when the vehicle has been parked for three hours or more, or if the vehicle has been driven less than a mile (1.6 km) at moderate speed.] A fast motorway run will raise them 3 - 4 psi