Take it in the for the recall. A new overflow tank won't help . It's a combination of crappy lines, the 207F factory thermostat and Ford not giving an F about upgrading the cooling system for the ST which produces a good +50% power of the original ST it shares the cooling system with.
And the recall will give you a new 180F thermostat, new coolant tank, new lines and they will check for head gasket damage.