Te air fuel ratio is maintained outside of the filter medium. That is something controlled by the ECU. If you give the car more air, it will give the motor more fuel. Hence, the ratio. 14 parts air, 1 part fuel. That formula is likely the same on the other 4 cars too.

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2006 X5 3.0L - Schwarz Black/Truffle Brown
Stock
But I keep it clean