"Restrictor"
You folks keep saying "it's not a restriction, the compressor discharge (or the throttle body, or... ) has a smaller area. The fact that there are smaller areas in other parts of the flow path DOES NOT keep an obstruction from being a "restrictor", not in a compressible fluid like air. If you measured the pressure at the turbo housing, you will find it is the highest of any point in the flow path. There is a pressure drop through the IC, through the up/down piping, through the throttle body, etc. on down to and including the intake valves. If there were no pressure differential there would be no flow. The "best" intake manifold will minimize this pressure drop, while providing the same flow to each cylinder. The more pressure the turbo has to put out, the higher the exhaust backpressure from the turbine, and the higher the temp of the air to the IC, so the intake system, including the heads and valves, should be set up to minimize restrictions/pressure drop. Pressure in the cylinder is what makes power, not pressure at the turbo.