Strange Garry's Mod Lag on Mid-High End PC

[Supervhizor]

For some reason in Garry's mod, I pull about 20-45FPS in multiplayer, and I should be getting much higher....
General Specs:
CPU: i5 3570k @4.2ghz
GPU: 2x NVIDIA GTX 660 FTW Signature2
RAM: 16GB Corsair Vengance 1600Mhz
Mobo: Asrock Z77 Extreme4
HDD: WD Caviar Black 1TB
PSU: Corsair TX750M

Using HwInfo and RivaTuner OSD in game, both cards have a core load of 5-10%, and CPU core 0 stays stable at about 60%, while the others stay well below 50%.Any ideas?

Edit: Might be worth mentioning that in the main menu and loading screens, I get 1200+ fps, and the CPU is 70% all cores, while the GPUs ramp up to 60% on both.

 

[i7Baby]

Try different game settings. Have a look on the Garry's Mod forum for similar problems.

Check the health of your pc with HWInfo - cpu temps OK?

 

[Supervhizor]

Try different game settings. Have a look on the Garry's Mod forum for similar problems.

Check the health of your pc with HWInfo - cpu temps OK?

lower settings lead to lower FPS for some reason. temps are fine. GPUs at 40C and cpu at 45C

 

[i7Baby]

gpu 45C is a bit high. Increase cpu fan speed

gpus at 40C is suspiciously low.

psu voltages OK?

 

[Supervhizor]

gpu 45C is a bit high. Increase cpu fan speed

gpus at 40C is suspiciously low.

psu voltages OK?

Voltages appear to be fine, and is 45C really that hot for an Intel chip? And under medium stress at that? (not like its idling) Last I checked, they can tolerate up to 105C.

Anyway, I'm fairly sure it isn't hardware, as every other application runs perfectly, including other Source engine games like HL2 and CS:S. Only Gmod is experiencing this problem. It didn't always have this probem either. I used to get 700FPS stable in game, then one day it tanked. Didn't manually change system settings or overclock anything (further than it already was) at the time either.

 

[i7Baby]

If the cpu was at 45C gaming then thats OK. I though that was idle.

You should look on the forums for clues.