and how much you are willing to spend before changing anything as there is a real risk of spending money for the bragging rights to say you did rather than actually improving the car. Or you can create improvements in one power range but subtract in another that turns out to be more important in your driving.
Just throwing some random parts that look good bought off the web isn't the way to your ultimate goal which should be to improve the car's driveability in the way you intend to drive it.
Rather go at it with a first this and then that and then finally this other thing. And when you are finally there, don't look at the total price tag because you could have bought a new 3.4 for the same AU$.
Some specific thoughts on making the car go faster . Its all the tips I've picked up over the years.
I'll frequently suggest renting some track time and working with an instructor to learn the capabilities of the car you have and improving your driving skill. Then asking those at the track what they did to improve their cars, did it work and why.
My 2.5 was in many ways more fun to drive than my 3.2 because I could put my foot down longer and harder. The 20% more power didn't help the fun factor as much as I thought it would.