Hey, can someone lead my to where i can find how much CO2 my car is blowing out ?

The problem is that i found now from a few websites "CO2 243 g/km" but my car is registered here as 343 g/km.

So i need to go down there with some proof to show that its 243 but not 343, and i cannot find any "HARD" evidence that right is right ! Like from a chrysler website or something.

Can someone help my out ?

Thanks