My suspicion is that this airbox was patterned directly after an original BMW Motorsport unit from the period of 1989 Gruppe A competition. Unlike the factory Wethje airboxes, this unit is not made in one-piece. The trumpets are molded separately from the main plenum and the two parts are then bonded together. The manufacturer airbrushes the joints with black paint to good effect. The joints are not that obvious in the finished product.

Furthermore, the inside of the airbox is smoothed out by hand after construction so that the finished product is quite functional. This airbox can be purchased from Germany for around $1000 (as of 2003). For an additional $300 a "kit" can be purchased which includes a bracket for attaching the throttle cable, a remote brake master cylinder fluid reservoir (the airbox contacts the original unit located on top of the MC) and an air inlet to mount next to the radiator in the same fashion as the original factory racecars ( e30shop ).

Note that fitting this airbox will require modifications to many types of strut tower reinforcement bars. Specifically the Sparco unit (that had been popularized via this website) will need to be "dent tuned" a bit in the region of the backside of the airbox. The power steering reservoir will need to be relocated a bit, the dip stick housing might need to be rotated in the block and as mentioned before, the brake master cylinder reservoir needs to be relocated. So this is not a straight bolt-on operation. Also, the air intake that comes with the kit will not accept the stock air filter. Here again the user must use some ingenuity in fashioning a solution.