I think the issue is about flow characteristics, keeping the mid plate seems to smooth out the flow and should result in better HP/boost level. I admit, this is conjecture on my part, it would be very cool to do the FEA work to prove/dis-prove this.
I wonder how a welded manifold would work made from a stock intake. Cut through the runners leading into the heads and replace the whole center sections with a 5" aluminum tube leading directly to the throttle body. It would end up being a big open plenum...
