how meny o2/lambda sensors are there on my car?
2004 wrx

im just about to fit a decat. im assuming there are 2 sensors, one in the manifold to control AFR and one in the downpipe to detect efficiency

dose the second one have any control over the ECU parameters?

iv got a tractrix. can i just turn it off?

 

There are 2, one in the manifold just before the up pipe and the other is after the last cat in the mid pipe.