PCSX2 Low FPS

Hello, I don't know much about the options and hacks for the pcsx2 plugins. I recently emulated MGS2 and the gameplay would vary greatly from 10 FPS to 59 FPS, some cutscenes were slow and some weren't. I've emulated quite a few games and they have almost all have sporadic framerates. Now I'm trying to play Simpsons Hit n Run, and it also runs slow, at about 20-30 FPS. I know that my CPU isn't the best, but I can play most games fine, and I am aware that emulating is CPU intensive, but surely the framerates wouldn't be this bad? :monkey:

Emulator:
PCSX 1.4.0
GSdx (MSVC 19.00 SSE2) 1.0.0 (Allow 8-bit textures, DX11 Hardware Rendering)
USA Bios v02.20
MTVU on

Specs:
Windows 7 64-bit
CPU - i5-2500k quad core 3.3 GHz
Graphics Card - GTX 670
RAM - 16 GB

Metal Gear Solid 2: Substance & Simpsons Hit n Run were both released on PC.