I recently had a Racing Beat cold air intake, RB header, RB power pulse muffler and Good-Win midpipe installed on my 2006 NC. Since then, I have noticed a loud popping sound when I shift.
If I shift below 3000rpm, there is no pop. If I really give it gas and engage the clutch at a higher than usual RPM (4-5k) it won't pop. During "normal" shifting, however, it pops once, very loudly, with every shift at the moment that I engage the clutch.
Also worth noting is that the car frequently throws the 0421 code for the O2 sensor warm-up time. I have replaced the sensor and the wiring harness and the problem still occurs. From the best I can determine by reading, nobody knows what causes this or how to fix it.
I would very much like to fix the popping sound, though. If it can't be fixed, can someone at least tell me that it won't hurt the cat or the muffler?
Thanks for your time,