there is some simple ways to make a bit better more power, bu it's not going to be quicker than your 300zx, unless you either turbo or supercharge the excel, which can be done by the way, and there is kits out there for cheap.
on the other hand, to make a little more poke out of it, just stick with the basics, Intake, Exhaust, bored thottle body and play with the computer if you can. also suspension mods will give you better response and more feel from the car, a good winner. things like short shiters shouldn't be overlooked either.
keep an eye out on ebay, heaps of stuff keep poping up for the excels cheap, things like extractors, exhaust, etc.
even the odd turbo kit from time to time,
oh, and since your an aussie, check out the aussie Hyundai forums
Hyper Auto Club :: Index
cheers