Your error codes tell us that your O2 sensors are sensing a lean condition and the DME is compensating by trimming the mixture to rich but has reached it's limit.
Typical causes:
Fouled MAF
intake vacuum leak
Mikefocke has a Boxter website with good basic troubleshooting for this problem with pictures. Check it out and then decide if you want to fix it yourself or pay someone else to do it. This is usually an easy fix that involves opening the engine bay and poking around the intake to see what vacuum hose is cracked or came loose. If everything is tight it is likely the MAF sensor is underreporting intake airflow info to the DME causing the engine to run lean.
Porsche mechanics often misdiagnose this as bad O2 sensors. In reality the O2 sensors worked perfectly. They reported a lean condition that could cause damage to your engine over time. Find the problem, fix it and then take her for a spirited Glendora Ridge run.
Good luck!