boost is a measure of restriction. Although you might get a lower psi of boost with a bigger intake manifold, you would actually be gaining power in certain rpm ranges because you're upping the efficiency of the engine's ability to make power. Same thing happens if you go from stock headers to long tubes, it'll make less boost but you'll make more power cause its less restrictive. A smaller manifold might be better for low end torque but with boost, you'll want high rpms, the more air you can flow efficiently is more valuable than low end torque
Not trying to show my hand too much but the combo I’m presently puttin together put out 630lbs of torque at 3200rpm. before boost. Im just trying to gain a better understanding of the size of intake and if there is anything to be gained by enlarging it. My Runners are 10.5 so from here the custom turbo cams I choose will dictate where the power will occur.