How do I cure popping noise from the exhaust during idling?

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My car is experiencing popping noise out of the exhaust during idle for a few months now. There is no CEL or anything. After start up and the idle settles down, it starts the noise. I don't hear it during normal driving. The only thing I can figure after troubleshooting; I swap coilpack #1 and #3, with no change. Then I unplugged #1, there was no popping noise; but it did cause a CEL due to unplugging #1. So does that mean there is an issue with cylinder 1? The plugs were changed about two months ago, and the injectors were changed last month. However since the new injectors were put in, my car drives great! (drivability, mpg, throttle response) Just need to solve the popping noise.