Totally normal.
Mine chatters whether cold or hot when driven a certain way (too much gas at low RPMs). I can make it chatter on command or keep it silent based on how I manipulate the throttle/clutch.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |