I don't have that game so I don't know how good it's running on GSdx or ZeroGS but those are the settings for max speed but sacrificing quality,sound(at low speed the sound is just annoying,you don't need it)and compatibiliy
DX9 or 10 Hardware depending on what card and what OS you're using(DX10 is faster)
Pixel Shader 3(2 if your card don't support it)
D3D Internal Resolution - Native
Everything other is off(except NLOOP Hack)
Texture Filtering is for better quality but on some games it doesn't decrease your speed when you use it as checked(not greyed)
Logarithmic Z and Alpha correction are fixes if the game requires them.
Mute and everything other is off
I don't know if when using as Output Module the 0-No Sound it requares to disable the other options too to have more speed but...use 0-No Sound and check
Interporation - 0
Disable Effect Processing
Disable Audio Expansion
Everything on and for VU-Skip values...those values are recommended for almost all of the games 0,0,2,4 or for REALLY slow games to gain little speed without bad frame skipping 0,0,2,1
INTC,IOPx2 and Default Cycle Rate are recommended but for more speed,enable x2 Cycle Rate or x3 but this really will reduce the compatibility.WaitCycle Sync Hack will give you speed too but it's not recommended to be enabled.
Enable all Flush to Zero and Denormals are Zero and on Clamp Mode use None
If you still don't get good speed then there's nothing you can to about it except buy new hardware.
PS.BTW disabling the memory cards gives you little speed boost too.
NFS games run slow on pcsx2.
try with speed hacks and GSdx NATIVE enabled. But if your cpu is slow then there is no luck.
Post your PC specs. But in any case, that game is available on PC if you desperately want to play it =]
SAGER NP8690 | i7-620M 2.66Ghz | 6GB RAM | ATI 5870M 1GB GDDR5 | FullHD 1080p 15.6'' | 500GB HDD 7200RPM | WINDOWS 7