Don't have a graph of a standard air box lid but this graph shows the difference between the back cut off the airbox and two large trumpets moulded in [apparently air needs a 3d shape to cause high airflow!] and a copy of a JHA airbox lid which has two long trumpets but smaller diameter.

Run 5 [blue] is better mid range and a slight increase at the top end.

Not sure if picture is attached!!!
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MC21 300
Aprilia RS250 track bike