just a note:

-cooler air is more denser than hot air and is therefore performance can be more optimised by some sort of apparatus either DIY or aftermarket to suck in cooler air.

-OEM airboxes are good providing the resonator has been removed to somewhat improve air flow.

-exhaust for B16 I would recommend 2 1/4" make sure this is ID (inner diameter) piping rather than OD (outer diameter) as your ID pipe would most likely be less that 2.25".

-as for muffler choices...again make sure it has the same ID piping as the B-pipe otherwise you would lose some bottom-end torque due to the decrease in back pressure!

Hope this helps

cheers