Most people say that bus bar corrosion will cause higher resistance at the terminals. When I replaced my bus bars, I noticed that the contact areas had no corrosion. That is, where the nuts tighten down on the bus bars, the metal was clean and shiny with no corrosion. I am confused why it matters that there is corrosion between the contact areas.
What you've observed matches what I understand, about the idea for the target nut torque and pressure between the nut, bar, and module stud being to create a gas-tight area that will not corrode, and probably isn't going to create any issue as long as the nuts and terminals have not been disturbed. Any increase of resistance there would be reflected in the "internal resistance" calculations done by the ECU, where you could see it. Taking the nuts and bars off and reusing, without cleaning, could be of greater concern, as you're not guaranteed to get all the formerly gas-tight areas, protected from corrosion, so nicely lined up again.
