Ok this might be a really dumb question but i havent been able to find the answer through google and ive searched for a few days. I got told that my o2 sensor needed to be replaced from the oreilly guy with his magic meter, so i purchased the o2 sensor because he said it was really easy and to just google it, i dont think he knew that i have an SI which i dont know if the o2 sensors are on the same place or not but ive been looking for one and cant find it anywhere except for the one underneath the car. So im wondering where it could be? I dont have stock headers on there also if that makes a difference. https://i.imgur.com/HVACiMM.jpg

 

Its under the car near the header flange. Not hard to get to, just need to jack up the car some and get a wrench on it

 

thats one of them i cant seem to find the second one?

 

Probably deleted the second one if the cat was removed for a test pipe, Do you have the stock cat or a test pipe? cause thats where the second would be, if so it was deleted and the wire and plug for that o2 was tucked back into the hole under the car. Also did he say which o2 needed to be replaced? down stream or upstream? And where is the o2 located under your car? the header or the cat?