Aadhi

I have Skoda Laura 2008 model which loses power when we are in traffic or slow moving. If we start the car at first time the rpm will not cross above 2.5 if we tried to cross the rpm shuddering sound from engine can hear. When we stop the engine and restart it immediately and accelerate the engine pick ups and car cross the rpm and power will be there. But after driving some time in heavy traffic or we slow down the car losses power and it will not cross 2.5 rpm again. Tried cleaning maf no response, fuel filters and air filters changed no response.after cleaning egr got little bit more power to drive for another 2000 kms. After some time it loses power again and need to re-start to get power for some time. Without power we can hardly touch 100 km in highway. And I noticed heavy fuel consumption and blacksmoke too. And the mechanic told to change ecm and check again. Car has done 1lakh kms And engine light was on. But showing maf sensor but tried replace with another one but same issue. Another issue some time abs and asr light will show.but go immediately after some time. Can any one help us to find the real problem. Tried several injector cleaning solution too.