Thats really interesting. I think (but I'm not 100% sure)when they run a car on the dyno, it's generally at full throttle and this can show a drop in low down torque. Talking to Northampton Motorsport I believe that the Duratec inlet manifold has vanes which operate at low revs to accelerate the flow. Perhaps the butterfly's in the TB has the same effect when they are partially open.
