I wasn't trying to say you idea is bad, but there is good reason nearly all intake manifolds designed for making power have plenums.
http://www.carbodydesign.com/archive...-engine-lg.jpg
That is one instance where dual TB's are deemed required. Look up some other designs and it's mostly that style on V type configurations where the intake ports spaced out on two different axes. I'm of the opinion that the dual TB setup on those is to maintain plenum volume without having to resort to shapes that hurt flow.
There is a mazda or something like that, that has equal length tubular cast aluminum intake manifold. I don't know what the design intent is though, as you diminish the ability to do resonance tuning without significantly adding to the flow properties.
As you increase the area of a TB, the flow increase is nonlinear. The same reason a single 3" exhuast has comparable flow to dual 2.25" pipes. Cheap 70 and 75mm TB's are abound for mustangs. If you can make a magnus IM, you can make it fit a mustang TB.