The guys in germany at Dbilas http://dbilas-dynamic.de/dbilas_eng/Einzeldrosseleinspritzanlagen/Einzeldrosseleinspritzanlagen_Strasse/DKA_S.php?ID=7# have a product for your e30/e36/e46/e34 which will allow you to have individual throttle bodies for each cylinder for your engine. From what I can tell they include the chip and all you need is a filter to attach to the new intake manifold.
They are TUV and ISO 9001 certified. So should be a quality piece. Some come with chip or a Dbilas camshaft for the price.
Check out these pictures. Only a few here go to their website for the whole list of engines/cars they cover.
For the m20b25 for a solid 2075 Euro including chip
For your m50b25 for a solid 2370 Euro includes chip
For your M42b18 for a solid 1450 Euro including chip