The front O2 sensor only reports what it is receiving and the rear one likewise reports how well the cat did its job. The problem may be upstream. The air mass may not be sensed correctly, the throttle body may not be reacting promptly, the injectors may not be operating correctly and thus the air/fuel mix is not correct, doesn't get burned and dumps too much unburned stuff into the cat for the cat to absorb.
So lets start...it is an '01 base or S? How many miles. Otherwise running OK? What tool did you use to pull the codes? Any others showing? Any recent work anywhere in the engine bay? Is the air pump that adds O2 just after startup working? Any hose leaks?
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Prior '70 914, '99 986 Boxster, '01 Boxster S
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