Not only was water injection a common feature of WWII fighter engines (for instance, German Daimler-Benz engines on Messerschmitt used a methanol/water injection called MW50 - it did provide more oxygen at high altitude and allowed higher compression since water vaporization takes energy and thus temperature away from the air-fuel mix - see for instance http://w1.1861.telia.com/~u186104874/db605.htm
, "Note on MW50" under the "performance chart"), but the GTA SA actually didn't use it. However, it's true that the system had been designed and experimented at Alfa on an earlier oil-pump supercharged engine, under responsability of Ing. Surace. It came back on the motorsport scene with F1 Turbos in the early 80s.
And indeed twin-overhead camshaft first appeared on the GP Peugeot designed by Henry in 1912. There was even there a precedent. I don't remember the name, but I have a picture of a huge (I mean 1.5 meter high!) boat engine from the very first years of the XXth century with DOHC!
The Alfa GP1914 not only had DOHC, but also 4-valves per cylinder AND twin-spark! You see what I mean...
Among the very innovations on production Alfas, one can spot the first alloy housing for final drive, on the 1900. When Alfa sent to Gleason in the US the 1900 diff case to have suitable gears fitted in, Gleason sent it back with accompanying letter saying" we are afraid you used the wrong metal for your final drive case", and Alfa had to insist they really intended to make it that way.
The other is indeed VVT, developped to cope with US emission laws without sacrifying the engine temperament. I would say first put into production in 1984, but that could as well be the first european-market application, with the first US model having been earlier. The US authorities calling Alfa to announce that at first try, the car was not eligible with the new norms, at the same time congratulated for having followed a way that didn't kill the original engine features.
On the racing scene, possibly was Jano the first to drive the (Roots type) supercharger with an intermediate gearing instead of directly from the crankshaft, back on the P2 in 1924. It allowed to adapt the supercharger speed to track requirement (er, a marginal improvement), but mostly it reduced losses and heating.