The most detailed diagram I can think of is the Porsche parts diagram. Heres a link to download it, just scroll through until you find the bumper diagram:
http://www.mediafire.com/?sharekey=c8260e4b7f10b09b6b21be4093fab7ace9993da6 7cc50b02c95965eaa7bc68bc
You might also look around at some of the DIY bumper removal guides with pictures. When I took mine off it was fairly simple, just time consuming. A few screws under the bumper, screws near the trunk latch, and the wheel well plunger things. Good luck!
