I don't know about the 4's, but the 6 cylinder airbox has a baffle in it to redirect airflow. It's in there mostly for decreasing intake noise. Taking the baffle out supposedly gives better airflow into the engine. Mine is debaffled. It is a little louder and I'm not sure if there are any gains, maybe high up in the rpm range? Cheaper than an aftermarket intake (like free).
__________________ 1995 325I, window tint, K&N, debaffled airbox, BMW #104 wheels, Nighthawk low beams, smoked side markers, smoked corners, smoked taillights, M3 stlye heated mirrors, various interior bits, Bosal cat-back.
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