from actual experiments ive done and ive seen other people do cold air intakes do nothing all they do is make your engine look a little cooler.
I tested them on my 02 mini one
i gave her a full service to make sure she was in top health
she ran a base run of 87hp dead on which i grant is not a lot
but its good for its age and mileage thats what the dyno man said.
with the cold air intake she produced 85hp its only a little drop but with a cold air intake supposedly you gain hp
And before anyone says thats a base model those intakes wont make any difference.
i tried it on my modified 2003 mini cooper s a couple of years ago
first pull she produced 187hp
we did this a few times and got a consistent 187hp so thats our base mark.
with cold air intake she made nothing 187hp
we did another pull and he lost 2hp 185hp
so personally i concluded that they do nothing but bling up your engine bay and make that cool whoosh noise thats it..
FREE HOT AIR INDUCTIONS DECREASE HORSEPOWER FOR A FEE
MINI ONE TORQUE FIGURES 135NM STOCK
MINI ONE COLD AIR 129NM SIGNIFICANT DECREASE