You can't change runner length with a throttle body. It's measured from the valve to the plenum opening. And at high RPM a shorter intake runner is desired.
"technically" you are correct, but in practice, keeping the intakes divided down the center for an extra couple of inches gives you a 1>2>8 intake runner, that has longer
effective runner length. ....vs what would be in a 1>8 runner system. just like headers, there is 4>1 and 4>2>1. which works better? depends on the application. Technically if you count the openings in a carb, you get 1>4>2>8 with a dual plane intake. (1 counted as the "common point" of air volume) and 1>8 with a single plane intake. The intake being open/common
under the carb
"effectively" makes the intake runner short, which in turn makes more power up top. The dual plane "extends" the
effective runner length by moving the common point of air volume up above the carb. My design takes (what i believe to be) the best of both worlds. sorry if i worded that horribly and confused anyone more than anything. hard to put in words.
Also, longer runners make more torque. This rig is for towing.
I admire your attitude, initiative, and desire to "build" something as opposed to just assembling things. It's an art that seems to be lost anymore.
i do this stuff everyday. unfortunately, its always been putting money in other peoples pockets. kinda tired of it. even it this doesnt work, the experience is enough for me. eventually Ill do something people will pay for.