White is typically lean, but not always. Lean is a bad condition for a 911 motor, if anything you want them running on the rich side. When the car is running lean, it will tend to run hot, which can lead to all sorts of problems. Here you see a valve that probably runs very hot...
Have your mixture checked with an O2 meter like this one:
http://www.pelicanparts.com/catalog/shopcart/MISC/POR_MISC_INNOVT-detail.htm
-Wayne