not knocking your build, but I've spent a fair amount of time researching and running design simulations on various intake designs and have cnc machined some runners for viper engines over the years. I applaud your effort in trying something new and I hope it works out well.

just giving an opinion that the runners seem to too tall and straight and there isn't enough plenum above them to draw air straight it. maybe its the angle of the pic. its also the reason the factory runs curved runners. its easier to package length in an arc. obviously not so easy to do in a weldment with a one off like you're doing.

also tapering the runners add a "ram" effect to the incoming air. as air is pushed through progressively smaller openings its sped up and this aids in fuel mixing. if you have a pipe like you;ve built you create a laminar edge along the surface of the runner of slow moving air. having a taper minimizes this. also you create a step at the head as the shape of the port changes, this creates an orifice which also creates a pressure drop. lots of engineering hours go into designing these things for optimum use. however there are always compromises, some of them are available materials so you build the best you can. again I applaud your work. I hope it works well.

if you'd like more info i'd be happy to help.