So after waiting 2 weeks for the DME...
Dealer called me and said that they've replaced it, reprogrammed it and it was still not the cause of the problem...
They've finally discovered that there was some shortage between the front fan wires and the some valve in the exhaust system (that's the explanation they gave me).
At least the car is back to how it felt before with no hesitations and good throttle response
For the valve in the exhaust system maybe they were talking about the valve in the muffler that opens up depending on RPM... but I'm not sure if this is electronically controlled or not