Modding the stock intake manifold (Upper not lower)

[vex]

Turbulent flow=good
Laminar flow=bad

Edit: Let me clarify it a little bit: Rough up the surface of the intake runners. The rougher the better. If you smooth out the surface of the runners you create a laminar flow which slows down the flow going to the intake ports. As such you will reduce the airspeed velocity which results in a lower torque curve.