P0172 Trouble Code (system too rich bank 1)

Getting this code for the last couple days. I was told that replacing the 02 sensor before the cat would fix it,but it didn't. The other 02 sensor probably isn't my culprit because it doesn't really monitor the air/fuel mixture. The car idles fine when cold and then it starts to stumble a little when it gets warm.other than the ses light coming on with this code,the car runs fine. any ideas? this is on a 97 Camaro Z28

Getting this code for the last couple days. I was told that replacing the 02 sensor before the cat would fix it,but it didn't. The other 02 sensor probably isn't my culprit because it doesn't really monitor the air/fuel mixture. The car idles fine when cold and then it starts to stumble a little when it gets warm.other than the ses light coming on with this code,the car runs fine. any ideas? this is on a 97 Camaro Z28

Anything that would make the engine run rich

Collapsed air intake duct.
Air filter element for being restricted.
MAF sensor for being installed in the proper direction and for foreign objects blocking the inlet screen.
For fuel in the pressure regulator hose.
For excessive fuel in the crankcase. Check the engine oil level. Change oil as necessary.
Inspect injectors for leaking (Bank 1)

Inspect injectors for leaking (Bank 1)

Especially seeing that there is stumble. Which you really contradict when you say it runs fine :dunno:

What injectors are in the car, stock?. Also, which side O2 did you replace, Driver or passenger?