o2 sensor running rich help

[sr20dude]

ok ive searched and search cant find the problem so if u can help me thanks.
ok so i finished my sr swap i drove it for a week and parked it for 2 weeks. before i parked it for those two weeks it was quite sounded amazing and didnt run rich now for some reason it runs rich and it back fires a little and when i unplug the o2 sensor nothing changes can find any vacuum leaks what do you guys think. i do have a test pipe but it didnt run rich before so why would it now all of a sudden. if you can help thank

[compactfean]

You wont notice hardly any change from am o2 sensor unless you have a wideband (the only differences will be seen on the widenand if stock o2 is out but not your a** dyno )
I would check all couplers clamps etc. And do a boost leak test

[IBustV8s]

if you have an exauhst leek anywhere above the o2 sensor then that will cause it to read more o2 in the exauhst and the ecu will try to compensate by putting more fuel through the injectors causing you to run rich. so check your manifold and turbo elbow for cracks. also check gaskets and make shore every things nice and tight.

[xekushnr]

Also, when an O2 sensor dies it typically runs rich. Do you have a CEL on? If it does it could give you an idea of where to look. Some oxygen sensors just go bad. The Bosch O2 sensors I have to sell at work are just horrible. Ive seen them be bad out of the box, I've seen them die in a week.