Mv can't help with the convertor. They slip. That's what happens. There is a lockup clutch in there. It Is nicer on the clutch to start a pull when it is fully locked , eg at 2800 rpm and light throttle then apply full throttle just be for run starts. Autos are a bit of a pain on the dyno...
Mv don't make convertors anyway, they get them done else where.
It would have been interesting to change the vct switch point, as the power really picks up at 5500 which is where vct turns off.
I noticed on the nistune site you posted your tune, can't you look at it and and see what he did with vct? It looks like if the vct was switched off earlier the curve would be nicer.
I don't think each each setup responds the same with vct switch point coupled with manifold and cam differences. For example I run type B's in my 2530 and they liked the switch point later, perhaps due to the extra air flow of the 30 or restriction of the stock manifold.