because its a dealer that told you that, it shouldnt mean anything unless that dealer is known to be crappy. In that case you should go to them then and go to a different one. There are plenty of good Subaru dealers out there!
None the less..... the sound might be normal if the noise is not audible from standing in front of the engine. If you put youre camera close to the injector, that may be the sound we are hearing. Try to get a video from a standing point there on the driver side. Dont put the camera or mic up super close to the engine.
If that noise is the same from a standing point, then it may be a few things. We would need year, make model, mileage, mods..... ect. So please do that and also fill out your profile.