Nobody really can. It might help push just a little more air up into your intake snorkel at higher speeds, but really they're for looks. Especially if you powder coat them a cool color so they're more noticeable behind your grilles. It has the same effect on performance that a carbon diffuser does for weight savings.... almost none at all.
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2022 X4 M40i - 2008 135i - 2015 F700GS
On Order - 2024 i4 M50
Scruffy's gonna die the way he lived... Mmhm.
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