We've done this with a Solus or Matco?Launch but not recommended.Also suggest to find an Indie who is a total geek on the Scanner subject. If not he will waste too much time getting this job done and it may make matters worse. As Mr.Stone wisely hints, it is a rare case that indicates the value of the Dealer. But often ,the younger Techs have little experience/interest in '20' year old Boxsters. If you personally visit the Porsche parts suppliers in your area, they will know who the Porsche-computer geniuses are in your area. They are the ones that buy a disproportionate number of modules, ECU's,Immobilizers and all the other electronics from them.
Good luck - you are close, you just need the right Indie now.
Hopefully you will not need this link:
http://www.ecudoctors.com/porsche-boxster-ecu-0261204790.html