[DsilverM550i]

Ever since doing a dual res delete on my LCI M550i about a year ago, the burbles have been loud and frequent (at least in Sport Plus mode). A few days ago, they abruptly became subdued (quieter and less frequent) and I'm barely experiencing any at all on decel (especially, as the engine speed blips up, as I come to a stop). It's almost as if I either changed modes and/or adjusted the engine sound in idrive (as opposed to an exhaust leak, etc.), when in fact, I did not. I've already eliminated exhaust valves as a possible culprit, as I coded them open and pulled the plugs. I'm also not experiencing a CEL, nor did a diagnostic I ran (on BIMMERLINK) bear anything out. Any thoughts?