Ethyriel_
I am running without any extra voltage, and have managed to get it stable at 2100 by changing... pretty much nothing, but it's performing statistically worse. 300 points lower in Time Spy, even if I let it cool down to 22C before starting the bench. I have the run that scored 19k saved and it was boosted lower during the run (Stable at 2070), but scored much higher. Still no idea what's causing this inconsistency.
It's windows. I've seen this behavior on a shunt modded 3090 FE that never even touched the power limit. You can tell if your score is going to be higher or lower by looking at the first 3 seconds of Port Royal. Once you've run PR enough times, you will know within 3 seconds if it's going to be a low or high scoring run.
You can also look at a Kill-A-Watt and see this behavior. During lower scoring runs, your card will be pulling less watts from the wall, even if it's never downclocking or hitting the power limit. During higher scoring runs, you will pull more power.
Another user said that his scores varied by as much as 1,000 points. And he was only able to fix this by completely reinstalling windows.
One thing you can try to do is to delete the shader cache in C:\program data\Nvidia Corporation\NVCache or something like that (First, set NVCP to NOT use the shader cache, then close all programs and delete the folder), then have the games rebuild the shader cache, but I have no idea if that does anything.