T_T - The Carbonio channels a significantly bigger volume of air to the filter as it has none of the compartments inside that the stock intake has. It's also bigger and has a more curvy flow.
Having said the above, I don't know enough about the physics to say that any of this matters, but I have seen dyno plot comparisons which seem to show that the Carbonio does offer improvements.
The actual Carbonio itself may be larger than the original intake, but yours is still connects to the OEM airbox, and there are other restrictive components beween the air intake and the combustion chambers.
There are a few other sites within the air intake system which can provide restrictions. On some cars, it is normally inside the airbox where restrictive sound deadening baffles are placed. If you know where to look, you can sometimes modify them yourself (indeed, I was doing this very mod on Mk4 Astra airboxes long before a highly regarded Vauxhall tuner, Courtenay, started charging for an identical mod
). However, the GTI airbox, which looks identical to the S3 doesn't seem to be too restrictive.
Other areas of restriction can be the intercooler (though this seems OK, as it is also used on the Ed30 and Leon Cupra), the MAF, the turbo (definately an area of restiction, as the Ed30, Cupra and S3 all have a larger turbo), the inlet manifold, and finally the intake valves.
