Borderlands 2 FPS drop

By doing a quick search (not sure this will fix your problem). This person does not have the same specs as your computer but maybe these could fix your lag spikes?

[Engine.Engine]

//PhysXGpuHeapSize=128

//PhysXMeshCacheSize=8

PhysXGpuHeapSize=256

PhysXMeshCacheSize=16



[SystemSettings]

//Fullscreen=False

//WindowedFullscreen=True

Fullscreen=True

WindowedFullscreen=False



[MemoryBudgets]


//AnimationMB=15

//AudioMB=10

//CodeMB=30

//LevelObjectsMB=4

//TerrainMB=4

//GameDataMB=3

//MaterialMB=1

//ParticleMB=5

//PhysicsMB=10

//ScaleformMB=8

//ShadersMB=10

//SkelMeshMB=2

//StaticMeshMB=10

//TextureMB=120

AnimationMB=32

AudioMB=16

CodeMB=64

LevelObjectsMB=16

TerrainMB=16

GameDataMB=16

MaterialMB=16

ParticleMB=16

PhysicsMB=32

ScaleformMB=32

ShadersMB=32

SkelMeshMB=16

StaticMeshMB=32

TextureMB=256

The above settings basically double the resource settings devoted to PhysX, as well as one setting for using Fullscreen mode. Windowed full screen mode costs some frames, so using fullscreen mode should net some extra FPS (I get around 15 FPS more using it alone). The above settings smoothed out my FPS to a steady 60 even in fairly high combat areas. The only area I currently have a problem with is one many others are as well, and that is the final area of the DLC "Tiny Tina's Assault on Dragon Keep".

This fixed the lag issue for another person on Steam Forums. His reply is:

Thanks for the clarification. Lath's tweak worked out well though, I'm getting much better framerates in areas that were previously trouble spots.

If this does not fix your problem, you can always try to delete your .ini files in your /Documents/My Games/Borderlands 2/WillowGame/Config and re-do your settings. I reccomend starting on everything very low/low and then work your graphics up until you it achieves a stable fps.

Sources:

http://forums.steampowered.com/forums/showthread.php?t=3147700

PS. This is mostly copy paste from the link..