The BMW E30 M3 was a very successful Touring Car during the late 80's and early 90's, as many folks already know. During this period of the BMW Motorsport racing effort in Gr A and DTM, the S14 engine was almost always equipped with Alpha-N engine management and a corresponding carbon fiber airbox (Alpha-N being throttle position based, as opposed to using a restrictive air flow meter). The CF airbox is much lighter than the cast aluminum two-piece factory plenum, and with the trumpets integrated into the airbox, it provides a much smoother pathway for air entering the throttles.

On the left we see one of the highest iterations of a carbon fiber airbox on a late model 2.5L DTM engine with 8 injectors. The first set of injectors is situated just downstream of the throttle plates, and the second set of injectors is placed towards the top of the trumpets. The second quartet of injectors would be phased in at high rpm to provide additional fuel and better atomization. Here the added four injectors are located on top of the intake trumpets, but there were also similar airboxes used at this time which had the added injectors located underneath the trumpets.