I didn't know this existed. About a year back I was looking at doing my own custom CAI, but got busy with a new little baby boy in our lives. (He already likes the D btw). Anyway, I'm guessing that it would have to be on the left side of the engine bay (looking from the front of the car). It seemed to me that there was plenty of room to put some piping in under there last I checked. It still bewilders me that no major BMW tuner has made a CAI for our D's. Countless ones for the 335i. Isn't there like 10,000+ D's stateside (2009-2011) that were made/sold?