Technical barriers during acceleration

[feelunstopable]

Hello everyone, i really try to explain my problem in english using google translator because my native language is russian.
This problem with Fiat Barchetta started after about 3 years of not using it, it just was parked and waited for me and i havent had this issue before.
So the problem is : while accelerating the car has some barriers, especially on the 1st and 2nd speed. The car is pick up the speed like it doesnt have enough power, with some kind of tremors. Sometimes the GAS pedal n the 1 st and 2nd speed even sinks for a second.
All filters are changed, spark plugs are changed, checked the airflow pump-it is ok.
What would you advise to check?

 

[StevePD]

Hi, You have tried the usual fixes but, is the fuel (petrol) the same fuel that has been sitting in the fuel tank for 3 years? Try some 98 octane fuel and possibly injector cleaner to clean the fuel lines. Also try cleaning the slow idle solenoid, this may be dirty.
Hopefully others will suggest more, good luck.
Steve D

 

[HP]

As above. Change the fuel filter, too.