Oxygen Sensor - Location and Part #

[KevinH1990]

2000 Boxster 2.7 liter engine with approximately 132,000 miles.

The check engine light illuminated yesterday. My Durametric downloaded two codes:

P1276
Porsche fault code 22 - Oxygen sensor ageing Delay bank 2 below limit value

P0133
Porsche fault code 15 - O2 sensor ageing ahead of cat. conv. cylinder (1-3) below limit value

From my research, I found that Bank #1 includes cylinder #1 and is on the passenger side in a U.S. vehicle.

Bank #2 is on the driver's side.

Here are my questions:

My understanding is that I need to replace two oxygen sensors:

1. The one before the cat on the passenger side.
2. I also need to replace one on the driver's side, but I cannot tell from the information which one. Should I replace the one before or after the cat?

The part number for the O2 sensor shown on my Durametric is 986.618.620.08. Noting comes up when I search on that part number. Please suggest a good replacement sensor part #.

Does the fact that I have to replace two sensors at the same time seem odd and suggest that there may be another problem?

Thanks in advance.