Just check that the port is clean and free of debris. I did this once on an HW35 and there was still a lip of metal on the inner side where the drill had not gone all the way through. I gentle ran a rat-tail file through the port and cleaned it off, instant 1 fpe increase in power.

I think they are best left alone, unless you have engineering facilities to put them back to how you found them, it is a critical part of the system and easily bolloxed up. Why does the Robb ream them? So he can sell reamers? Sticking a venturi in or countersinking them is going to change the volume of the port and could mess things up big time.