You can do some mods to your engine, and since you're from Canada, finding parts won't be too hard, because in the US, there are many parts for older Alfas. Just check ebay and you will see...
As for tuning - intake runners:
- All Alfa 2.5 V6 12V & 2.0 V6 TB & All 3.0 V6 12V (except QV version) engines have 38mm intake runners
- 2.5 V6 24V & Lancia 3.0 V6 have 42mm intake runners
- All 3.0 V6 24V & 3.2 GTA & 3.0 V6 12V (164 QV model) have 45mm intake runners
So for intake runners, I would suggest you get 45mm ones. I've also seen from one US alfa specialist, that they even make custom 50mm intake runners for the Busso. Might be good to check it out.
Next the intake manifold:
- All V6 12V have 2l capacity intake manifolds
- All V6 24V have 2,5l capacity
And yes, you can fit the intake manifold from i.e. a 3.0 V6 24V model. I fitted it on my 2.0 V6 TB engine along with 45mm intake runners, so it can be done! You just need to modify it a bit, so it will fit. And use an adapter plate for the throttle body. Since the 24V manifolds are a different shape - on 24V engines, the manifold is also used as a valve cover for 1-2-3 cylinder head, which on the 12V engines it is not. There it is just a manifold. So you need to cut that piece away, modify/weld on the three legs where the manifold sits on the valve cover, and that's it.
Next the exhaust:
- Exhaust manifolds from 12V engines are better designed than on 24V models. So using stock ones is the way to go. But you can remove or replace the factory cat, because it munches quite a few horses. Also you can fit a bigger diameter exhaust completely. 2,25" is the stock size, going 3" would be hell of a lot better
While you're doing this, you can remove the middle silencer, because it has no role whatsoever (it is not silenced, it only acts as a resonator), so there are some gains to be had as well. And of course a lovely backbox, to top it all off.
- Best cam upgrade for your engine would be to use the 3.0 12V QV model cams (200hp from 164). But finding them will be next to impossible
- It is larger than on 24V models as it is, so going bigger will be expensive. You can buy 100mm TB from ebay, but if it will work with your TPS sensor, I don't know... Stock unit will be more than enough for the horsepower you can squeeze from that engine.
- People say you can use a MAF from old BMW's (E28' or E30'), but I wouldn't bother. Stock unit is good for massive amounts of airflow. Ask Flavio, he used a stock MAF on his 400+HP GTV, and was only at ~60% of the MAF's limit... Also, using a different MAF would mean you would have to program your ecu to work with it. It isn't plug & play...
- Porting your heads is also something you can do, to gain some performance. I once found a site about porting the exact engine you have written by an American fellow. Might be good to search for that, as it was a good read.
And for the end a good chip tune and you're done. It isn't scary, you just have to remove the eprom from the ecu, read it, rewrite it, and voila!
So all in all, you CAN tune this engine. Sure it would be easier like others have mentioned, to just replace the engine, but doing something different is always a nice challenge
Bear in mind that AR155 V6 Ti produced almost 500hp with the same engine, so there is room for improvements with your stock ~170hp