I have a 2010 Equinox LT 3.0 with 87,000 miles. I put new aftermarket O2 sensors in during the summer. After a couple months they were not reading the right voltage, they were all replaced with AC Delco. At the same time injectors 2 and 6 went out and they were replaced. The pending lean codes eventually cleared on their own after these repairs. I recently put two new pcv valves in. Two start-ups later the check engine light came on with P0171 and P0174. The light went out the next morning. Those two codes are still stored and now I have a pending P0300. Are these related to the new pcv's or should I be looking into this further?

Thank You for any help.