Hello everyone. My 2007 Outlander's "Service required soon" light came on, got it checked at Autozone and it is getting a code P0171 system too lean bank 1.I have cleaned the MAF light didn't go away. I just received the left and right upstream O2 sensors, I read that it's best to replace in pairs. Both upstreams together or both downstreams together. I am having trouble finding where they go. Autozone said it takes 4 O2's and I am only seeing the one in the very front of the engine and the one underneath right before the catalytic converter. Any idea where the other 2 are and which ones are the ones I have found? Any help would be greatly appreciated. Also, I am doing process of elimination obviously.