Successfully tapped fuse 5 in a August 2012 build '13 M3. Used one 3 amp fuse, left the other slot empty, and everything worked once I put the black wire to the ground screw. I passed over that step and was confused about what to do with it. Once I read the instructions again, it all worked. Now I just need some felt tape for this fuse box and my rear camera wires to stop the rattles.
Great write up!
Current: '13 E92 M3 Euro Delivery 9/4
Wife's: E39 M5, E36 M3, E30 M3
Gone: E86 M Coupe