Yes, there is a big difference. The MULF module is for the MOST based cars (all the new body style cars, like E60 5 Series, E65/66 7 Series, E63 6 Series, and E90 3 Series). The MULF will not work in the E38, E39, E46, Z4, X3, and X5.

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2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input