When adding this kit does the auto on feature still work? Also can you run the 55W kit? The Oem hid's are 55W so I dont see why not.
I have a '07 so I'm not sure about the auto-on, but in terms of the 55w vs 35w:
While it is true that a 55w HID kit will draw less power than a 55w Halogen bulb once it is warmed up and on, it draws significantly more power on start up to get the bulb on. So while you **SHOULD** be ok with a 55w kit on stock wiring, it is HIGHLY recommended to run it off of a harness that supplies the power.
Think of it this way, why risk a major repair (re-running all your headlight wires) when a 35$ harness can prevent all the problems.
The other thing to consider, (unless you have the 2011+ with HID headlights, which I doubt) is that even tho the 11+ has projectors, they are designed for halogens not for HIDs. While you won't be glaring every single person on the road, it isn't optimal. That is why in my '03 with halogen projectors I chose to go with a 35w kit, while it is no where near my retrofitted '07's performance it is better than halogens and doesn't blind every driver on the road.
Also, a word of advice, DO NOT go above 6000K in color temperature, you will actually receive less usable light that your halogens would provide. Unlike a **LOT** of the people on this form that think the deep blue headlights are the coolest thing since sliced bread, they are actually worse than halogens, and every time I see one on the road I flip my highs at em, and laugh at how ridiculous they look.