My engine (o-360A1A) ussually backfires through the intake when I pull the throttle abruptly to idle. I have adjusted the idle mixture so as to minimize it but it isn't eliminated. I have also checked for leaks in the induction system. I have primer lines to the #1 and #2 cylinders and even though there is no indication of a leak I am wondering if they could somehow be the cause. Also, I tapped off of #3 cylinder for both the manifold pressure (MP) indicator and the MP input for the LASAR controller. I'm wondering if that could have something to do with it. The engine performs fine other than this. Starts easily, develops full power smoothly, and leans normally during cruise. All the way back at idle there is ussually this low popping like 1 or 2 of the cylinders is not producing power. It stops immediately when I bring the throttle forward. I have the standard carb. Has anyone seen this kind of thing before?