O2 sensor readings from torque.

[Rakin]

Hello guys. It's my first post here, I've been browsing as a guest for quite a while now looking at the threads related to the 1NZ-FE and this forum has been quite helpful in helping me gain more knowledge about my motor.
Firstly I must confess, I do not own a Yaris but a NZT240 Premio which consists of the same 1NZ-FE powered drive-train as the Yaris 1.5L under a different sedan shell.

Okay so I've dropped in a recon 1NZ a few months back and I've been noticing recently that there is a strong smell of unburnt petrol coming out of the exhaust pipe. O2 Sensor and MAF sensor was the first thing I checked because they control the fuel loop. The O2 sensor in the Manifold had done more than 100K KMs and was completely burnt out and filled with carbon so my mechanic replaced it. Now I could not get a new one at that time (Lack of availability of the lesser common parts here) and had to settle for a recon one. Note car did not throw a CEL.
I noticed the smell was slightly less than before but still could smell it from the driving seat. I connected my OBDII ELM327 Diagnostic adapter and did a graph view of the O2 Sensor at the manifold (It's the only O2 torque would read anyways). I'm attaching the graph below, is it normal for the O2 to jump around like that? Throttle was held down at 2800RPM.