I’ve recently learned that the precats on the Spec V’s can start failing and hurt the engine, so I want to get headers for my ‘06. But doing research I’m a little confused. I’m new to cars in general, so apologies if this is a total newb question. Where does the spacer go? Some of pictures show...

I discovered that my o2 sensor plug had fallen out one day so bought and installed a new one, this fixed the wrx boxer like engine sound coming out of the exhaust and temporarily turned off the check engine light. Unfortunately this only lasted for a couple miles of driving before the sound and...

I need help on how bypass the o2 sensors on my QR25DE I purchased an aftermarket header to delete the precat and now I keep getting ses codes for the 02 sensors. If anyone knows how to bypass them please help me out and tell me what I need to do.

i bought i megan header to replace the precat. I still have the second cat futher downstream. will i have to do the non fouler trick and would i put the non foulers on the first or second o2 sensor?

Greetings fellow sufferers. My lovely Primera with QR25 engine continues to behave like a spoiled kid - happy for a minute then grumpy and pissed off for no reason. It generally starts nicely from cold then deteriorates to being hard to start and having a lumpy idle when warm. I have already...