Well, the negative overlap is relative to what really makes power on the setup at hand. I feel its several components paired together resulting in that being the optimal tune for that setup. At first I thought it was the IMRCs, however, once they open at WOT, they are of no restriction. I honestly think its the long tube runner and plenum volume of the stock intake manifold paired with the short tube odd pairing of the stock exhaust manifolds attached to large catalytic converters. All of these components paired with larger valves, cams, and better flowing heads, requires a abnormal tuning of the VCT for the car to function efficiently. Imagine having a race engine and them slapping a cork in the intake and exhaust, VE is going to take a massive dive and to get the car to operate, massive tuning changes will have to be made for the decrease in airflow. That would be my guess. However, no one has proved this yet. And tuners that have tested this argue that it isn't the case, however, they have NOT tuned VCT correctly, which leaves me to believe the potential is still there. I learned to tune on VCT vehicles, so I know how well it can be adjusted to increase VE. Most Mustang tuners I feel come from single cam non VCT engines, so it's all new technology and tuning to them.