R30 6cyl 2.4L cheapest performance upgrades

i'm buying an 3A Racing Air Filter, what else will give me better performance? an engine service? high-octane fuel? i have like 360,000kms clocked up on it

what do you of me getting this: http://www.spiralmax.com/

I was told my R30 has turbo, it has a boost gauge on the dash, if it does have turbo it isn't stock.

Do I have to have turbo to use the SpiralMax and TurboTwister exhaust thingy? if not, will i still get performance increase from it if i dont have turbo (just in case)?

I am in Australia, so consider I would have to find SpiralMax in OZ, or find an alternative available in Australia, or import it, etc.

Should I get a lightened flywheel?

(yes I want to race on flat off-road areas against my friends).


p.s: what cool things can i get, (i'm currently deciding on racing gloves, racing pedals, and some sunnies maybe, i already have some black raybans that look good) what other "trinkets" or stuff like that can i get?

http://www.drakkan.net/skyline.jpg
(not smashed anymore)