93 Chevy c1500 4.3 tbi running rich ?

[Buck 01-02]

Hi, 1993 4.3l tbi auto
I just purchased this truck about a month and a half ago, & there are some issues with it, one is it seems to run rich at idle you can smell it in the exhaust.

I have replaced the MAP & coolant temp sensor, I have a brand new single wire (stock) o2 sensor Im putting in tomorrow. Do these trucks only have 1 oxygen sensor ? And do you think the new o2 will help ? Cat looks fairly new maybe a couple years old judging by the welds