Fiat Linea (1.3 MJD EP) Acceleration Issue!!!

I have been facing a weird issue with my Fiat Linea 1.3 Multijet Emotion Pk. Occasionally, when on a long drive on highways, I have noticed that the car looses all acceleration for a short period. At this point, there is absolutely no response from accelerator or gear shift (downshift or otherwise). It is as if the vehicle gets stuck at that particular RPM and speed with only slight deceleration.Obviously, on braking the vehicle, it loses speed and there is no issue with braking. Also, Upon aggressive downshift (downshifting to achieve RPM above 3500-4000), I am able to regain normal acceleration. There is no error in diagnostic software when checked at service centre. Further, it is very difficult to replicate the error in workshop due to unpredictability of this problem. Is this a turbocharger issue ? I personally do not think so because this condition happens at any RPM whereas turbocharger only kicks in after 2000 RPM. It could be a problem with the injectors but once again any such problem would be more consistant and would show up in diagnostic software. Finally, I suspected a problem with fuel line but Fiat service centre staff ruled this out due to no smoke (white or black) at the time of problem. Has any other Linea owner experienced this error and was able to resolve it ? Can the gurus shed some light on other possible problems. Thanks in advance.

URL: