just got done installing my AA bov and wanted to add one thing:
the vacuum line might be different depending on the year of the car (im not too sure), in my case (2009 e92 335i) the vacuum line going to the factory dv is only one that splits in two forming a "y" shaped fitting with one line that goes to the engine and the other two go to each of the dv. when you install the bov you are left with only one vacuum line (provided with the bov kit) that runs directly from the engine to the bov. in this DIY is different because the vacuum line runs from the engine to a "t" shaped fitting which splits one line to somewhere not pictured then to a "Y" shapped fitting then to the factory dv from there. this can be confusing for some as it was for me. thats all, great diy op.