Sorry was not checking this forum for a while. Some kind of popping sound when your turn your amp on is normal as long as it is not too loud. What you hear is the spark of the factory radio and amp turning on which then is amplified by your sub amp. As explained in the previous post the remote +12v wire provides a +12v to the factory amp slightly after the radio has turned on. Here you used the same remote +12v for both factory amp and sub amp therefore you have both of them powered at the same time. Several things you may want to check though. A loud popping sound could be due to a loose ground. Did you properly ground the high level input ground wire? Also check if you did not put the gain too high. Try to reduce the gain on your sub amp. If you still hear the popping sound and if it really bothers you a delay circuitry should indeed help. Some circuits will mute the sub amp and some others will mute the speaker for a short period of time until the radio and amps are on.