have been changed over 4 times during the past six months on my e34 520i.... i complained it being jerky before, recently replaced fuel filter and rear shocks (bilstein). my mechanic diagnosed it as a spark plug fouling up problem, or at other times , spark plug electrode wears down too fast.... any ideas as to what the problem might be?... am tired of replacing spark plugs too often especially since i do low mileage ( 200miles a week) currently using bosch sparks...

ps: are the bosch super 4 spark plugs any good... pricey but seem to be good..?