They are certainly cool, and would be neat to have a set, but the factory ultimately stated that you don't need them. Just set the main linkage to exactly the right length, then put the ones on the throttle bodies so there is no pre-load and they all come off idle together.
Check this thread.
Interestingly, Grady Clay, one of the great Pelican board technical contributors who sadly died a few years ago, has the last post in the thread, and he still thinks the protractors are valuable. But if Porsche decided they weren't needed because the mechanics couldn't use them properly, I'm not so sure I'd trust myself to do it properly...