Regardless of the reason, I can understand why a 996 is louder than a 986 due to drivetrain layout. If the chatter really is "normal," I'll just live with it. Its not obnoxious, but it is noticeable.
I know this thread is old but I know what the answer is: Transmission gears are rattling against their mated pairs. Removing the dual mass flywheel took away the isolation of crankshaft torsional vibration from the gearbox. At low engine speed compression strokes and then power strokes, slow and then increase crankshaft rotational speed markedly, causing gears in the transmission to bang forward and back against each other making this sound.
When you disengage the clutch (pedal down) the transmission is disconnected and the noise goes away.
Using a driven disc that has a spring hub is the best answer I know of to lessen this noise.
Hybrid Mode
