Yes, it's a G.M. engine, "BADLY REWORKED BY ALFA." However, the only cars that have any connection with the "Alfa Romeo Proper" are the 916 GTV's and Spiders, the 3.2 GT. and the 147/156 GTA's. 147 and 156 twinnies are loosely connected to the early twin sparks - they pulled the heads out of their museum and reproduced them at a time when the competition started to get too close, but they used a Fiat Steel block. I'm afraid you are two generations too late, if you want a real Alfa engine. So, your choice is limited to the aforementioned Busso powered cars. The diesels are great engines, for what they are, but were developed by Fiat Power - Trains.
If you want the 159, 3.2 to perform like an Alfa, find a way to get rid of 600 kilos, open the V.V.T. Phasors up and pack them out with spacers to mimic the Busso's Valve Timing. This will enable you to run on a decent grade of engine oil to protects the mechanicals. Then design an interface box to fool the ECU into believing the V.V.T. solenoid valves have set correctly. Make sure the car is a Q4 and be prepared to work the the gear changes as of old, perhaps changing the gearbox ratios at the same time. Economy probably won't be any worse but emissions will go through the roof. Christ it will be a good engine though. Indeed, it is a good engine, just Alfa F----d it up. One of the prettiest designs still to this very day, pulled early. A really decent chassis, pulled early. A car that goes round bends; Q4, like it is on rails, pulled early. A car that is almost impossible to un-stick and so easy to recover, pulled early. Why?
Crap Corporate Thinking. The average Joe Public has more love for the Alfa Marque and it's heritage, than those Wooden Headed T---s that fill the boardrooms at Fiat. The greatest service they could do for Alfa Romeo is to sell it to - Mmmmmm? Anyone. Never have financial decisions impacted more on the reputation of this once great company. They will never be allowed to compete in Maserati or Ferrari's territory, so what is the point. A chap who had a 8C at an Auto Italia day complained bitterly about the amount of Maserati components under the bonnet. They hadn't the common sense to change the identity of cheap plastic components with a stamp which said Alfa Romeo.
The new Giulia is a recipe' car, designed to fit in and not to compete. with other models within the Fiat Empire. They are not interested in taking the fight to their competitors, just in making sure Alfa "Know Their Place". they will never be allowed to steal the thunder of Maserati or Ferrari as they did of old. And all B.M.W. and Mercedes have to do is step it up a notch. And then Fiat will return to selling the cars based upon the Badge, rather than their performance.
I love Alfa Romeo. I loath Fiat.