Given your two hour distance from a dealer, the dealer might be kind and be willing to share any necessary programming codes with a local independent.
Hopefully someone in your area can give you the name of a good local independent shop. Where I live, there are several independents who can reprogram cars and the dealer have been willing to share codes.
The one ECU / immoblizer repair shop I am aware of is at:
Select the ECU DME, Immobilizer Removal, or ECU Performance Upgrade that fits your Porsche Boxster from 1997 - 1999 - Specialized ECU Repair. Several forum members have used them and said good things about the service. Try giving them a call and describe your problem. They might be willing to suggest what is causing the problem might be and some things you can try. IIRC, they sell refurbished ECU and immobilizers and repair them too.