BMW 2006 325xi e90 N52 125K - My car makes a strange noise from the drive side under hood. Noise heard when pressing gas pedal and goes away once I let the gas pedal a little bit. It comes back again when I press the gas pedal and goes away once I let the gas pedal.
One could hope it is a heat shield. Are you a diy guy? take a rubber mallet and bang things along the exhaust to see if anything is loose.
My guess is some sort of exhaust system problem as well. Does your engine have a turbo? If you described what the noise sounds like, that might sus up some more ideas here.
I will post the audio today.