The AFE is open on top but box is quite close to the hood and at the front of the engine. During acceleration the flow will be primarily through the intake and cooler. The other aspect of cold air intake is higher flow. The X will adjust fuel flow to match greater flow of air. The result is some gain in HP and torque. I went with Dinan, don't think AFE was available at the time. Their performance gain claim on 4.6 is 13HP and 12lb/ft or torque. FYI--Dinan version does have a closed top. The engine will sound much better as a side benefit.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas