Adjustable cam timing pulleys would be a nice addition for almost any engine. They essentially do the same thing that VVT does (shifts the powerband), but you can only set it to one rpm at a time versus how VVT constantly varies the cam timing. I'm not aware of any place you can buy these for the Aveo though.

Forged pistons are not necessary IMO. They don't really provide any gains per-say. They are simply stronger than normal pistons. This allows them to hold up to higher boost pressure essentially. However, when you get new pistons you can also change compression ratio which can be used to run more boost, or have more off-boost power. So, the bottom line is unless you are planning on really building up the engine to handle a ton of power/boost, I'd just stick with the stock pistons. I think you'll get plenty of fun out of them.

The biggest thing I'd be shopping for right now is probably a programmable ecu. There are many options out there from piggybacks to standalone systems. You'll need to choose one and understand how it works to tune it (or pay someone to tune it).

I'd also highly suggest Maximum Boost by Corky Bell. It'll go through all of the things you'll need and teach you what you need to learn to put a turbocharger on a car. Seeing as this will be a custom one off setup, it'll save you a lot of time and money by knowing better what you're doing. I have his book on supercharging and it was invaluable when I was doing work on my car.