The K&N Short Intakes that I installed didn't have that extra chamber either.
I wouldn't worry about it.
It might have to do with noise reduction. I think the car is a lot louder when I stomp it.
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Bill
2010 370z; Tour/Sport; 6mt; BlackCherry/Grey;
318 rwhp; 265 lbs rwtq.
To view a list of my mods, click
here; To view a photo journal of the mods, click
here.