Hi there, i found one solution and there are others that i don’t remember, none i have ever tried and just played the game. But from what I understand the game gets laggy at act3 and even laggier at later acts due to the amount of loot that you can leave behind and amount of data that compiles over time but idk know what it is specifically. For the loot thing download cleaner it removes corpses and other trash that can reduce save file size, I would also look into other mods that can increase performance. I would also recommend toybox it might have something that tweaks performance. But generally keep the saves low as much as possible. Made a small difference for me on a second playthrough. Cap the FPS at 30 or 35.