So I have this cute problem where at any seemingly random point in the game, I get some serious fps drops. The problem is that this isn't performance related, it's some sort of bug in the game or my PC, wich I doubt.

The thing is that his happens only at very specific points in the world, where the picture doesn't change at all to justify any kind of fps drops let alone somethings this extreme. These screenshots clarify.

The only thing I did in that was tapping the W key to take a seriously small step forward and it's like I'm walking into a crowded town in the middle of fireworks. If I take a small step back, it goes back to the original framerate. From the 2nd screenshot onwards, the framerate sticks to those 40-50 until some other point, and before that, I get some clean 120fps. So it's something very defined at that point in the map. And this happens on multiple places, somewhere walking over the water flow bit just before that spider cave is also another spot where it triggers this fps drop.

Also, the game used to be fine. Then I starded messing around with the Skyrim 2k textures mod, and got that problem. Unninstalled the game clean, no configs, nothing other than that save game, didn't work. FORMATING the whole PC, didn't work. No hardware changes at all other than a new mouse, something that shouldn't mess around with something like this at all.

Does anyone have any clue at what this might be? Because I'm dying to play this game and this is bothering me like hell.

i5 @ 3.3Ghz
Asus GTX 560ti
Asus P8Z68-V board
8GB DDR3 1600Mhz

Thanks to anyone that tries to help.

EDIT: Couldn't add the links to the screenshots, great... But in case the text wasn't clear, right before the cave with the frostbite spiders right after a new game, while still trying to escape into skyrim, at one point in that cave I get 120 fps. I take a small step forward, the picture doesn't move at all more than a couple of pixels, and I get 50fps. Past that imaginary line, I get a 70fps drop, and it happens multiple times in the game world. What's happening where I'm getting less than half the performance my PC is cacpable of in those places? Game is fully updated, formated the computer, tried plenty of options, nothing worked so far.