I'm with Mark on this one... why design a turbo that is bad on purpose?
Get a great responsive turbo and you control boost targets in the mapping to limit the torque in certain areas, but this is ultra responsive when called on the rest of the time.
and
Butty - you will not lose anything over the VF43. As good as that turbo is for an OE turbo, I overlaid some graphs of my old VF43 and the now much bigger MD321V and it whoops it in all aspects. At no point in the power graph does it let you down or deliver less than the std turbo but when it wants to and you allow it - it nails you back in the seat giggling.
Oh and btw you dont need to split the block to put pistons in
