I've alway wanted to know how WRC/GRP-A YB achieved 600nm of torque and only 300bhp.

I know they where high comp and they have 32/34mm turbo restrictors but can someone explain the science behind this, ie how a restrictor effects power and not torque etc What sort of boost did they run?
I've seen a IHI turbo and they are tiny! it just amazes me the torque they produce! Has anyone got a plotted power graph for a WRC engine? would love to see how the power and torque rise on these and where the peak power is etc

Is there anyway of appyling these methods to other YB's combinations so you could have for instance a 400bhp engine with 500lbs of torque??