I have a 05 Nissan 350z that has always had a P1274 code on/pending

Question

I have a 05 Nissan 350z that has always had a P1274 code on since I owned it (purchased used). If I erase the codes, there is always a pending P1274 and even sometimes a P1283 code comes up (not always). Could these be a faulty O2 sensor for sensor 1/bank1 that can just be replaced? Or something unrelated to the sensors themselves.
I live in upstate NY so the temperature fluctuates here often, but the car is stored for the winter and only brought out during the summer, but this year I am having a lot more trouble with it for passing NY inspection. I just don't want to spend the money on replacing the O2 sensors and then see the codes still come on and it be a waste of money.
Car had some after market parts on it from the previous owner (not my choice), one being a cold air intake, which I thought could be contributing to the problem. I did just clean the filter and the codes still come on pending right away.
Any help would be very appreciated. No one has been able to give me a solid answer. Thanks

Answer 1

Start by clearing the  Mixture Ratio Self-Learning clearing procedure, there is a hard way to do this and an easy way.

easy way disconnect the battery for an hour or so. hard way go through the steps 

http://nissanhelp.com/diy/z/projects/nissan_z_clear_self_learning.php
 

if the code comes back, replace the both bank 1 and 2 sensor 1. there may also be an ECU update for it.