I have a similar problem - when pushed hard/very accelerator pedal car is not accelerating, but the car is drowning (choke - I do not know which word to use). If you press the pedal lightly and submit gas gradually, then the car starts to accelerate. This bothers me a little when overtaking another vehicle - not enough power or lose power.
As a solution to the problem of the service I was told to spew oil into the fuel.

So I now read about a 2t oil in the fuel, and will try it when next filling up the car with fuel.