I get noises like you describe when free revving the motor in between shifts, especially when the clutch just starts to contact as my foot is coming off the floor or when I stab the pedal to rev it up. Two things going on there for me:
1. A rattle/grinding/buzzing between the engine and transmission as I'm overlapping my pedal inputs, basically eliminated as I became more deliberate and figured out how to shift smoothly with this car.
2. The throttle body is by wire and makes an alarming noise when it snaps open, see this post:
http://www.ft86club.com/forums/showp...20&postcount=3
If neither of those sound right then go to the dealership, it sounds very reproduce-able by your description. Good luck
Edit: I forget about the VVT noise that Dezoris posts about below, that's probably what you're hearing.