Nasty99SS

This pass weekend we were looking at my car trying to find a exhaust leak. We reved it a few times and started hearing this weird knock coming from the back of the intake? The knock is really loud when the car gets up in the RPMS, sounds like its on top too...doesnt sound like its down in the motor at all. Its really hard to explain over the internet but any idea what this could be? collapsed lifted? any suggestions would help guys

Thanks Mike