I've noticed my Supra's, even being rebuilt to specs, have a weird noise. It's a soft noise that you don't really notice, kinda sounds a little like a sliver of piston slap.(If you drove the car and have never driven it before, then you wouldn't notice it) It only happens for me between, 1100 and 1500. But you'll never hear it anywhere else over the rpm board.
Note: (Also, i've noticed it in other inline 6 motors, like jeeps, and ford trucks.) maybe a coincidence.