Quote:
Originally Posted by snakey
Gotcha. The kit does talk about a relay.. I'll research a bit into that not familiar with it.
The HID kit talks about one too so I'll look into how that works.
To answer the fog light question. . It just looks cooler. 
snakey
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The factory wiring is generally designed for a certain load, and fuses are designed for that load as well. You can put a bigger fuse in to compensate for the higher draw, but now the wiring which was only originally designed for X amps is being pushed harder. Too much and you will melt wires. This is the reason for a relay.
(Yes, I am sure you can get away with it for a while if the load isn't significantly higher and I am sure some have even done it.. but it's a new car, and worst case scenario for melting wires is an electrical fire. Why chance it when it's cheap and easy to do it the right way?)
A relay is basically just an electrical switch. Instead of the fog lights being ran off the headlight power, they are ran straight off the battery (like everything is) and use a lead from the headlight power to switch the relay 'on'. The headlights just tell the relay to switch to 'on' - they won't actually supply power to the fog lights.
With HIDs there is another factor, and that is that they draw a good bit more power when they first start up. If there are other things on the circuit trying to draw power as well - they might not ignite.
Google how to wire one up, I'm sure there are thousands of diagrams online.
As for the fog lights looking cooler when on all the time; obviously a personal opinion, but most of the world laughs at people who run their fog lights constantly. And, it can be obnoxious to oncoming traffic. And, lastly, it is illegal in many (if not all?) states to run them when it's not foggy out.. but that is clearly not enforced ever.