Ok guys so I know i have to install a o2 sensor which I did since I got one from advance that cost me $77, now my question is, My downpipe has two 02 sensors bug,
Do I need to install two of them, one that suppose to be the factory one (the one I just bought) and another one for tunning? or the one that I got in advance be good enought for the tunning?

Also is the one that I got in advance good enouth, or I should have got a better one? I just got it as a factory replacement one.

 

Well depending on what engine management system you are using and who tunes your car you may or maynot need the stock o2 sensor. when your car is tuned a wideband 02 will be used. The tuner will either use the extra o2 bung in you have to intall a wideband or a "sniffer" in your exhaust

Edit: to clearify you will not need 2 stock o2 sensors, you may not even need the one you bought. just cap off the extra 02 bung