if theres a big lump in the VE table then yeah probably is a bit odd....
i know the VK EFI manifold on a certain motor had a really odd high point at lower rpms, then dropped off to a normal ve curve, i can only assume it had some super good efficiency at that point in the inlet
No matter what the question is, the answer is always more horsepower!
The exhaust on the one /'s you tune, are they dual exhaust or single outlet, the one I tuned was single, was 4.9 a/f low end, 5.5 - 5.4 seemed to achieve max power top end.