Loud POP in exhaust when shifting. Cause?

[Gatlinator]

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,
Garrett Gatlin

[Brian]

Pops normal with header change....see thread on pops top of the forum page or at this link Pops were always there, you just didn't hear them with more closed exhaust system. These often run a little rich as well, and you could lean it a bit and get more HP with a reflash.

On the code, rare but we do get reports....see the other PO421 thread and link to trying spark plug anti-foulerto back that second sensor a little more out of the stream of gas flow.

[Gatlinator]

Thanks for the information. I did some reading and I feel a lot better about it. My main concern was for the cat. I didn't want the shock from the repeated popping to damage it.

How would I go about looking for a shop that would tun/flash the ecu the make the car run leaner? The exhaust definitely smells rich and I could use the extra fuel economy.

Thanks again!
Garrett