First, calculate the difference in % of your new gears compared to the old gears. Then, if you want to dial out the factory speedo error, add another 1% to 2%.
If you got 4.57s, you have increased the ratio from you stock 4.10s by 0.47. So, divide this by 4.10 and you get an increase of 11.46%. You need to dial up +11.46% +2% to get a total of about +13.5% on the Yellow Box. Now go and find a cop who's willing to pace you at an agreed speed. You will now know whether or not you need to dial in more or less. But by now, you're going to be pretty darn close.
Whatever speed you decide to get paced at, you can then see what your speedo says. Just figure out how many more or less % to put on the Y.B.

 

Thanks Xviper! Does it matter if I have 18" wheels?

 

Wheel/Tire diameter can make a difference in your speedo. This just means the basic calculations Xviper gave you could be off somewhat. You should still be able to fine tune your speedo with the yellow box by having someone pace you or using a GPS.

 

The diameter of your wheels is not nearly as important as the diameter of your wheel and tire together. If you got the correct tire aspect ratio for the wheel so the the overall diameter is the same as stock, then there is no need to worry about them. However, if you did not get the correct aspect ratio, then you will.

 

I'm good to go then, thanks for your help!