My System:
Motherboard: Gigabyte GA-K8U
CPU Type: AMD Athlon 64, 2400 MHz (12 x 200) 3400+
Memory: 2048 MB
Video Adapter: ATI Radeon 9600 / X1050 Series (256 MB)
3D Accelerator: ATI Radeon 9600 XT (RV360)
Using: WIndows Vista Ultimate, Logitech RumblePad 2 Controller

I can play the game fine with no lags or anything like that when im in Queens, Brooklyn, Manhattan or the bronx. However, after i cross the water into New Jersey, everything slows down and starts to lag. I have to try to drive back into city just so the game is playable again. Anyone have a clue?

My guess is all the houses and trees are lagging it, I'd try tuning the graphics settings.

You have a fairly good computer except the CPU. Since your CPU isn't the fastest I'd suggest you to go to Options --> Gameplay ---> Decrease the amount of cars (Every car on the road is cpu controlled and since dpl has so many cars this adds to the cpu processing.

As DriverKid said you should also go into option and lower the quality of a few things, particularly the resolution. Or turn everything as low as possible and everything should work and then turn everything slowly up and continue testing it until you find the right setting for your pc.

Also considering New Jersey has to process so many trees, fence segments and clutter all at the same time would course this to happen. But the cause shouldn't be to significant.

But I guess it all depends on the computers setup. Anyways Good Luck!

If you run into any other problem ubisoft support are there to help at any time to.

Just go to support.ubi.com