Re: air box
It's a resonance chamber,
It helps to remove noise "the induction effect" and is supposed to also do something
with smoothing the air flow into the filter. The induction kits generally take these out as you get more noise, and the airflow properties change with the kit anyway....
on the 156 the 4 pot engine have these chanbers before the filter on the GTA it's after. The v6 inlet mod (using the v6 and jtd inlet pipe on a 4pot) removes them
I'm sure someone who has done one of these kits already wil have more info.
Alfa V6 - the ultimate aural pleasure
Simes - the Alfaowner formerly known as Alfa156man