Intake valve noise (video in comments)

[Ufamizm]

Im not quite sure what it is, I got the car about 3 months ago but i only started to really notice it after i drove it home from school 2 months ago (1100 miles non stop). Because it only does it when the cars revving back to file, i feel like its one of a few things. intake valves, spark plugs, or fuel injectors. Has anyone had a similar issue they they were able to resolve? I took it to BMW for brakes and to check this problem, and they gave me the whole "Couldn't replicate the issue, or its not a problem" BS that they always pull.