Hi there,
Just thought I'd put my experience out there, in case anyone else is tearing their hair out trying to resolve performance issues in Satisfactory.
I am an enthusiastic user of the Efficiency Checker structure builds, and had used (according to satisfactory-calculator) 157 different instances across my factories (for reference, I'm about to finish tier 4 of the Space Elevator).
After removing all instances of this mod, my FPS jumped from 30-35 up to 120. Not sure what exactly caused it, maybe it's running a recalculate too much, or the ways in which I was using it was causing an unnecessary strain on my system.
Tagging @Marcio <Checkers/Copier/WallSup> for their consideration. And thanks for your work with the mod, it really is a life saver for my factory optimisation needs.
I can provide further details, or a copy of the save if needed.