O2 sensor change...finally

[spanish pants]

Seems like a silly question to be asking, but....
I´m finally going to get around to changing the o2 sensor on my 525i. I don´t think it's been changed in a long time (previous owner was a gypsy, and they have to be the biggest skinflints i have ever known)
The part should be here sometime in the next week.
I just wanted to know if there are any noticeable differences before and after the replacement?

[ak-]

I have an air fuel ratio gauge in my car.
Last month, after car gets to proper temperature it would run stupid rich(cruising & idle 10 AFR). To the point where blipping throttle in a parking lot/releasing clutch would cause it to run slugish and/or shut off.

Suspect was o2 sensor or TPS. Replaced o2, and car is cured and back to normal again.

m20 motor.

[spanish pants]

I have an air fuel ratio gauge in my car.
Last month, after car gets to proper temperature it would run stupid rich(cruising & idle 10 AFR). To the point where blipping throttle in a parking lot/releasing clutch would cause it to run slugish and/or shut off.

Suspect was o2 sensor or TPS. Replaced o2, and car is cured and back to normal again.

m20 motor.

AF gauge might be a fun toy to have in my car, but it's above my skills to do that sort of thing.

As for the car. It seems to run just fine but there's a slight fuel smell from the back side. I imagine this may be from the old o2 sensor.