Bad Smell B Class after acceleration

I have a problem with a B Class. After get the car runs with long acceleration and speed up to approx. 80 - 100 kmh, bad smell/ odor come inside the car. The smell is likely an exhaust gas smell. But i don't know from where it came. The inside circulation mode for A/C system is also worked at that time. Is anyone has ever figure out the same problem?

Thanks,

Daniel - Indonesia