I would say you could do it with the cams removed so all the valves are closed, then vacuum out what was left behind. However anyone that port matches to the gasket especially the PI gasket since it is so oversize has no clue how much worse their velocity probably is. The best intake port is usually a smooth taper down from the plenum to the bowl and you have to think of the intake manifold as an extension of the head. From what I saw in those pictures it looks like he made 2 bell mouthed junctions at the gasket which when bolted together is a big bubble area inside of a tube (bad for flow in the tube) A generic "gasket match" is probably the most common mistake by newb home porters I imagine especially since the magazines spout it so much.
BTW - You need to work the bowl of that head also to increase the flow, what he did didn't change the flow in the head I would imagine since that isn't where all the restriction is.