Coolant lines run between the back of the motor and the Turbos. Other than coolant tank, the lines from turbo to block are the most prevalent to leak. Ones on back of engine are the hardest to get at. My bet is it's the one on drivers side. You'll need to pull the crossover pipe anyway to get better reach behind engine.
Many threads on this. Do a search and you should find plenty of info.
I stayed with the Ford orange coolant. Dependent upon your climate, mix could vary.
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