Some V8 Maserati motors had a Bosch distributor supposedly shared with certain pre-electronic Mercedes V8's -- perhaps just the big 6.3s (others had dual point Marelli distributors), and these were known to occasionally crack the wire which is attached to the points, causing a loss of spark to the four cylinders controlled by that set of points. This is less likely than the injection problem mentioned by the previous posters, who have genuine M-B experience, but it might be worth your time to check the continuity of the wires in question anyway,.