Read about what the different motor tuning companies can offer for more power here.
.: Road handling :.
Read about better road handling for your 156 here! This one is a must and is the cheapest way to tune your car. This is actually a complete article from the Norwegian Alfa Romeo Owners Club magazine (Alfanytt).
.: Parts tuning :.
There are also things you can do for the car body to get higher performance. With reduced weight and more powerful brakes, you will improve the track handeling a lot! Read here about the companys that offer these parts.
.: K&N mounting guide :.
K&N have made this great how-to guide for installing Induction Kit on a Twin Spark Alfa Romeo 156.