this post is old but looks like it was never solved. did you ever find out why it was popping and sluggish on one side? i have the same issue except mine only backfires loudly when accelerating not at idle. and it has poor power on one side and the other is powerful. this power of one side switches at random and is not stuck to one side. every now and then the power will come to both sides but its only momentary. why was this post neglected? i read all the way through hoping to find a solutions so i wouldn't have to make another post but now im sitting here wondering what happened?