[Htci]

Mine made the noise while idling so I could just press upward on the muffler with a stick of wood between the floor and muffler and the noise would go away. That allowed me to conclude it was a mounting issue however only visual inspection will allow you to pinpoint the issue. First step would be to safely get under the car while it’s running and look and listen for any rattles and leaks. Could try using an engine ear. Check tightness of all mounting points and Muffler clamps. If that doesn’t resolve I’d remove rear bumper so you have a clear view of this mounting point. Again, this was easier for me because it happened even while at a standstill at idle.