Originally Posted by Savington

First and foremost, turbo size, because it's quite an exhaust restriction. Secondly, the intake ports and manifold. Changing the manifold to an aftermarket manifold with velocity stacks has proven to prop the torque band up quite a bit in the last 2000rpm or so, which greatly improves flow and top-end power.

Ironically, everything that you can do to increase flow in a turbo motor will reduce the restriction that we measure as boost.