cough

Good evening I am a chauffeur based in York, I use a Mercedes s 350 bluefficiency 2010, I have a recurring problem, here goes, sometimes when I accelerate whether gently or more the car feels numb, the next time it feels like a rocket, when it is numb it is often followed by a cough or misfire...

Not mine, but I was tootling along the A299 in Kent this evening when a beautiful looking 20year old 280 SE whispered past me at about 80. Little bit of grey smoke drifting out of the exhaust, but it looked the business. Then he had to slow down for traffic and a bigger plume of blue smoke came...