ive had my car for like 3 years now, ever since i bought it, there was no 02 sensor on the bottom end of the exhaust manifold like most other cars. i was wondering if this is correct, or should get the right exhaust manifold and spend a arm and a leg to get an o2 sensor. its running a gsr stock header right now, with no hole for the 02 sensor

 

^^

 

Are you getting any codes?

 

There isn't an o2 sensor in the bottom of the header, just two near the top. At least in my car anyway