I have a 1988 740 Turbo that is blowing smoke at stoplights, or when I idle it for cool down before I park it. Normally the smoke goes away if I rev the engine slightly or if I have a breif bout of hard accelleration, but it will come back. It is white smoke, so I know it isn't burning oil, and it doesn't smell like oil. I am assuming it may just be gas that isn't fully burnt, but I have no way of knowing. I just replaced the spark plugs, should I look at replacing the wires too? Or could it be an issue with the timing, and should I replace the timing belt?