I went with the fuse box because when I turn the key off I want that sucker OFF.

You know how the old head unit loved to stay quasi on sometimes.

Its up to you and should work fine using the wires in the harness. I just don't trust it completely and want to make sure I never had a weak battery again ever so I hedged my bets with the fuse tap.

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Just BMW's - All cars and trucks was two pages long
1994 318is
1997 528i
2000 323i
2001 X5 3.0 auto
2005 X5 3.0 auto
2011 535xi auto
2013 X5 xdrive35 Turbo
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Aftermarket E53 Radio Install