Technically speaking, the larger you can make the inner diameter of the TB, the more air you can push through it.
That being said, I'm not certain on the port/polish. I've done a set of aluminum heads(back in the day). But that was before bolt on, so I can't say it helped/hurt.
I'm thinking you can pick up a stock TB for cheap, P&P it, throw it on, and see if there is any change.
