I have been filling up the bottle for the radiator every month it seems. I know that used to be a sign of a bad egr valvle, but I can not find one on my wifes 4 runner.

 

No egr on the 3.4.

If you have rear coolant lines they can be a source of leakage along with a lot of other places, like under the throttle body, behind the engine, the heater control valve, the oil cooler lines and so on.

Also check out 'pink milkshake'