Malf Code 45


I thought GNs are black
Okay so....Autozone MAF # 3 failed on me a few days ago. I limped the car home. I received MAF # 4 LOL and installed it. I noticed on my A/F meter that car was running hella rich. So this morning on the way to work CEL comes on. I jumped the pins and got a code 45. I looked up the cause for it and its pointing towards bad o2 sensor. Now here are the symptons. When I give the car about 50% throttle o2 readings are extremly its pinning the gauge to the rich side. Then when I let off the throttle it dips to the extreme lean side. I have no scan tool (try not to rip me a new one okay) cant afford a Scan Master right now. Im gonna replace the o2 today a see if thats the cause. Worst case scenario does anyone think that another poorly calibrated MAF could cause this?