I'm getting codes for p0133 oxygen sensor slow response and p0171 bank 1 too lean. The car runs fine, and according to my AFR gauge it's not running rich which I'm told is what happens when your o2 sensor goes bad. I just got the car tuned last week and a couple days ago these codes came up, not sure if it's related or not but I e-mailed my tuner and he says I just have a bad sensor.

I want to make sure it's bad before I change it, so what do you guys think? I do have one small issue which is at idle the car will SOMETIMES go full lean and start having a bouncy idle. But other than that no problems.