If you can pop the hood and listen while it's idling and have someone slowly raise the RPMs for a moment, can you get a better idea where the sound is coming from? If you can hear it more from the upper firewall area on the passenger side, it could be the fuel pump. The injectors are noisey too, but that should be more even on both sides. Those are audible while standing still. For me, the waste gates did not rattle and make a lot of noise until I was driving. Even after the campaign, I still hear my waste gates but the rattle is all but gone.