A few basic background questions:
1. When did you install the Cobb dp, at what mileage and how many miles are on the car now?
2. Related to above question: How long after the dp install did the problem(s) with the sensor - first and/or second sensor begin?
3. I think there are three bungs on the Cobb downpipe. Which bung did you use for that first sensor?
4. And yes, as someone else noted. please log the voltage to that sensor and report the data.
5. Did you AP tune before or after your dp install and which was most closely related to your sensor problem? I'm trying to find out what your setup was before you started throwing this code.
A thought: Since the sensor is also dependent on the ECU for that voltage signal and since you are running AP, you might just want to try a quick reflash back to stock to check voltage in the event there is a problem with your tuning map. But, if your answer to question 4 above shows normal voltage at the ECU, then the problem sounds like it's not in the ECU but in the wiring, connectors or the 02 sensor. Makes me wonder if the wiring or connector issue may have pre-existed your first failure and that that sensor might not have been bad.
A second thought: As another poster pointed out issues on the intake side can throw this code too. Besides sucking in unmetered air, another possibility I've seen on other cars with this code is a bad or dirty MAF sensor, believe it or not. Some Bosch cars like Volvo, Saab and VW's can throw this code with a dirty MAF sensor. While I don't know of a dirty MAF can throw this code on our cars, I'd be checking that too along with checking for air leak sucking in unmetered air.