Well
1) It would seem you need to send out YOUR ECU for them to redo, so plan on some downtime for this to be done
2) It is only legal in California on "off road" use - like a track. Likely won't allow you to pass NY emmission which come very close to Cali standards
3) It will certainly VOID any warranty
4) Since you send out your ECU, I am sure the Porsche Diagnotic equipment will know you've tampered with it when you need to have regular maintenance performed
5) What happens when you take the car for a long trip and can't find the octane you specified on the re-flash? Does it ping to death and kill the motor?
6) Without muffler/headers and intake revisions, I don't see you squeezing "10%" (or nearly 25hp) out of the car aws advertised. Sorry.
7) If you haven't already, you could join PCA and learn how to really drive your car well instead of simply "modding" it to go faster