Yes, I want to open it up. I believe the restriction is where the
round port transitions into the rectangle port? I was going to
open the round portion to 1.65 then reblend the transition.

Here are the ports on one of my old intakes, these ports are
huge. This manifold outflowed the heads quite a bit but still made
lots of torque and a very strong top end.

I want to duplicate this with a TPI using stock components if I can.

You did see the pic of my base where i went through the wall right. I was trying to do exactly what you're talking about, i was trying to open up that canted outside wall to match the round runner that leads into that bend. I broke through so fast that it blew my mind.
In other words, like i said above, there just isn't enough meat in the runners to open them up by any significant amount. If you really want to try to push the envelope i have to suggest you do a lot of measuring of wall thickness. Off the top of my head i'd guess you're not going to find much more than 1/8" thickness anywhere except near the flanges.
Give it a go, just keep in mind how little room for error you have. If you can find a way to fix that transition w/o breaking out, everybody here would love to see it.