Have you Burped the system after your coolant flush? Air bubble maybe stuck behind thermostat... check around vibration dampner for moisture/coolant , i have the same car in the garage and also found usage of very small amount of coolant (not enough to worry about) over a weeks time.. but will overheat when idling
i found the alternator bracket is also a coolant housing for the heater core hoses.. this housing plugs into the block(center of motor,a plastic 90*tube under blower pulley) and into housing that water pump is attached to. it may look like this--
