CNC Mill Mark Removal in Intake Port

Imo, the “correct” way to evaluate changes to the intake port surface finish is on the dyno, not the flow bench.
And I don’t work on anything where doing that kind of R&D is cost effective.

I’ve seen what I felt were pretty impressive results from smooth, and rough, and cnc finished ports.

I don’t feel like a different surface is going “fix” a bad port.

If I think of some of the better combos I’ve built, where I ported the heads myself, those heads had the smooth finish.

There was a thread about this subject on YB a few years ago, and I remember Chris Uratchko commenting that one of his best builds had smooth ports.