I installed a perrin uppipe on my 02 wrx, I was wondering if since that uppipe delete the O2 sensor will that harm my car?
There's no o2 sensor in the uppipe. There is, however, an EGT probe which can be deleted (if that's what you're referring to as the o2 sensor) Now the Front o2 sensor is located in the exhaust manifold, passenger collector side (right before the uppipe). That should not be removed.