C250D when travelling at say 100 klm I tried to overtake a slower veh. I planted the foot, transmission went down 2 gears, revs went up but speed did not increase. Very slowly got to 110 and I just managed to get past.
Very dangerous, has any body else had this problem or any ideas?

 

Problem fixed, while the mechanic was replacing the fan belt he inadvertently knocked the MAF indicator from its position in the air intake. I was checking oil etc before a trip and noticed the loose MAF hanging down, put back in and found another 100 HP very happy now.