Here is a link to something on a UK Boxster board from 3 years ago.
http://www.boxa.net/forum/index.php?showtopic=15803&st=0&p=155605&#entry155605
If the link does not work, this is what I said.
"That is not good news - hope you can save your hub.
It looks like the bolt is 12 mm diameter x 1.5 mm pitch. You should replace it anyway so buy one and take it with you when you pick up the tap to verify the size.
I do not know what you call it in the UK but we call it a thread restorer. It does not cut new threads, it bends the old threads back into shape if they can be saved. The same type of tap is used to restore spark plug threads in aluminum heads.
If you can save the threads and torque the bolt to specs then you are lucky, otherwise you need to replace the hub or have the threads drilled out and put in an insert. I have no personal experience with the Boxster hub. Because this is a safety/brake item my dealer would just replace the hub.
Torque specs are 63 foot pounds or 85 newton meters."