so long as the water outlet from the turbo is connected as close to the inlet of the water pump as possible, preferably AFTER the thermostat on a 4age, in conjunction with the inlet of the turbo connected as close to the outlet of the water pump.. then you'll have best flow.
in practice this is not as easy due to the available water connection points. so unless you want to tap into the water pump housing on the front of the block to feed the turbo with cooled water.. (good luck, the cam belt runs above it!) the next best place is an outlet coming out of the engine block.. and since there are none.. (unless you want to remove the water drain from the block)

next best is water outlet from the head ie original 20v radiator outlet or 16v radiator outlet or temp sensor block on back of head.
i think the main point here is that the thermostat acts like a restriction to the whole system. (like a resister is an electrical circuit) so for best water flow of an auxiliary water circuit, you need to be running in parallel with the restriction (thermostat) like the cabin heater does. (feeds from head outlet and returns after the thermostat).
unfortunately the heater circuit is taking hot water and cooling it whereas ideally you'd want to take cool water and heat it.
so in a perfect world you'd tap into the water pump housing (outlet side before it enters the block) to feed cold water to the turbo and return it into the top radiator pipe so it can be cooled before entering the engine again. but again good luck on this.. this is cam belt territory. also means every time you replace the water pump.. you have to tap into the new pump housing.. or unless you can put a fitting into the water pump backing plate on the exit side?!
soo.. unless you want to dick about modifying water pump housings.. fit the turbo feed from a water source on the head, and fit the turbo return to a line that feeds back into the water pump after the thermostat ie the heater return line or the thermostat bybass line.
in theory this is not the *best* route, but in practice, this is what factory water cooled turbo systems run. at normal operating temps, your coolant system still has enough capacity to absorb heat from the turbo before boiling point.
does this simply awesome pic kind of explain the system using rwd 16v thermostat housing with the 20v head? ... (substitute the cabin heater for your turbo)
