I wouldn't worry about warranty that much, its essentially a pipe and a filter, if you install it properly it shouldnt cause any problems. If you're really worried about warranty and want piece of mind, just go with the F-Sport - F-Sport parts wont void your warranty.
For lights, if you want to match your stock HID go 4300k.
Lowering your car an inch in the back definitely won't cause any problems - you'll still clear most if not all inclines easily.
Hope this has been helpful!
Hey Terry,
Thanks or your advice. Are you sure the stock HID is 4300k? Just a reminder I have the 2010 Is250 f-sport. I have a feeling that the stock bi-xenon lights are 5000k. I've tried looking online but its useless. Not even on the website.
Mike