It is possible. Take a look at my last few pics, yes, I know, I don't have your engine, but it all depends when & how you get your final speed, and you should easily come to the same fuel consumption. First wait for the correct engine and oil temperature and pressure, and then you can enjoy every horse in your Alfa, not to much thinking about the consumption
If you drive mostly "shorts", then you can only dream this kind of consumption...
And, something that is also very important: tyre pressure, don't go under 2.4 bar, as this is the original tyre pressure recommended by Alfa Romeo for 159, and use nitrogen instead of pure air.
New Alfa's were not designed & engineered to be driven like an old retired car. Alfa is a state of the art, in diesel engine & design.
Do you talk to your Alfa? If not, then this could be the reason, why you coud not get lower fuel consumtion