back fire damage question

Hi all. I need some help with what I suspect is a self inflicted problem . In decarbonizing my 383 Impala, I slowly fed a can of SEAFOAM into the intake down stream from the throttle blades using a very small diameter hose. I have done this on previous occasions with this and other cars with very positive results. On this occasion, however, the engine popped back through the intake once but I was able to keep it running. There was a little smoke in the engine bay which is not usual for this procedure. The exhaust usually smokes like crazy if you over feed the seafoam which I know can be dangerous. I let the car sit about half an hour (off) and then took it out on the road to blow out the crud and it ran very well. After a few full throttle runs and some cruising I brought it home and, at idle, noticed what sounds like an intermittent, irregular noise in the intake manifold area. It sounds sort of like a high pressure air leak or a light tapping but not all the time. The engine through a code which I have not had checked yet. All the valve springs and rockers are good. QUESTION: What would be damaged in the top end of the engine by a pop back? EGR valve? Intake gaskets? All hoses are sound and connected. The car runs good but the noise indicates something is not right. Any suggestions would be very much appreciated.
Thanks in advance,
4stroke