i just discovered MB sold me the wrong spark plug. Its for a 1.8 litre car & not 2.2 litre. The difference is 0.8mm gap versus the correct 1.0mm gap. I think this should not effect the car shaking but only its feul effeciency right or am I wrong. Returning them tommorow & hopefully can rule this one out & concentrate on the wire & coils only.