Had magnaflows on my truck. Same thing, no other issues (EFI and tuned) and if I got into the 2,500+ RPM range and let off it would pop on decel. Below that no popping. Freeway decel it would pop intermittently. No leaks, nothing broken, plugs / wires fine not rich or lean. Just the way it was. Had aerochambers as well and same thing.