the clutch fan should be pretty 'stiff'. if you spin it by hand (while the car is off ) it should stop pretty quick.
if it doesnt stop quickly, the fluid in the fan is most likely gone. so wen the prop spins the fan doesnt spin with it all the time.
so it could be moving, but not fast enough.
also the radiator could be clogged. it will flow, but not fast enough.
i went through this just a little while ago.
swapped the fan over as its was pretty much free spinning, then found the radiator channels to be blocked, to the point where there was
about 2-3mm for the water to flow.
also with the new turbo, the water lines? used the standard lines? the bango bolt pin hole could be blocked a little?