First of all, I have no real experience of this prob on Alfas, so don't take my word as gospel.
As I understand it, at part-throttle most modern cars are running "closed loop" - the ECU monitors the exhaust gasses and compensates the fueling and ignition to get a good clean burn. At full throttle, they go open loop and resort to a preset map for fueling. If the injectors are bunged-up, then they may be providing enough fuel at part throttle due to the compensation, but at full throttle the preset map is too little for a blocked injector?
Try an injector clean? Could also be a duff sensor somewhere? Find somewhere local to read fault codes from the ECU? (Alfas do have a diagnostic connector don't they????)
Again, these are just ideas, not firm suggestions.