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Hello all, I know this topic has been beaten to death, however many of these threads lead to more questions than answers. As far as single turbo water cooled applications, what return water lines need to be retained. The water feeds are self explanatory, and the returns are too to a certain extent, my questions are mostly focused on the returns on the intake side at the rear of the block. I have attached pictures below from a thread that asks a similar question, however the answers are of a great range and indecisive. My question is, do both water returns under the plenum need to be retained? As far as my knowledge is concerned, the pictures below of the water returns under the plenum, have the arrows showing the wrong direction of water flow. As far as I know, the metal tube under the plenum that goes to the heater core, provides water flow into the thermostat housing, not away from the thermostat housing. The other picture, of the engine outlet, leading toward the radiator inlet, looks to have the correct arrow showing flow showing the turbo water return. The front return makes sense when the thermostat is open ONLY, as that is when water flows through that outlet. The rear return under the plenum that connects the water tube that connects to the thermostat housing, also makes sense, as it provides flow when the thermostat is closed. The one that confuses me is the one that connects to that water chamber connected to the intake plenum. This fitting seems redundant to the one on the front of the intake plenum area. Is that connection "needed" and what is its fiction?