Amazon.com: Add An Amp Amplifier Adapter Interface to Factory Car Stereo Radio System for Subwoofer Bass for some BMW Mini Cooper VW Vehicles - See compatible vehicles listed below : Electronics
MOST Fiber Optic Amp Interface for BMW E90, E91, E92, E93, E60, E61, E81, E82, E83, E84, E70, E87, E88, E89
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Upgrading BMW Amplifier. How to replace and adjust? Check it | BimmerTech