Hi Jolly,
Intercoolers are always well spoken about with regards to increasing performance. (If you are unfamiliar with what they do, they basically cool the air that a turbo pressurises before it enters the cylinders in the engine. The cooler air is more dense, therefore it means that an even higher volume of air is blasted into the engine for a better combustion under pressure.)
Altering the fuel injection can sometimes help if it isn't quite "timed" correctly.
Fitting an air filter that allows maximum air flow into the engine can help.
Erm, and that's all that I can think of for now!
-Pos