Originally Posted by Corsairprime

I run the Berk HFCs on my '14 Nismo. No CEL, made sure the exhaust to manifold seal was not leaking. Try the Permatex® High-Temp Red RTV Silicone Gasket Maker if you are thinking about going this route. I also swapped the secondary O2 sensors for new ones about 18 months ago. One of them was going out, or getting lazy about registering values to the ECU.

Best of luck.