I think this sound started today after I pickup from dealer for pcv heater recall. I don't remember hearing this sound when driving to dealer 2 days ago but I don't drive this car much as it is my wife's.

Sounds like it's coming from under #3-4 intake manifold. Not DISA valve, nor valvetronic solonoid.

Side note: the rattle noise at idle under the air filter housing is loud and hard, which wasn't there before. Not sure if the tech forgot some thing that cause this rattle and the weird engine deceleration noise when car is not moving (P or N). The same sound also present during test drive so it's not the driveline.

Anything else under there that could cause that grinding sound after the engine decelerate? TIA.