dreamr33,
I bought same car and started doing similar modding just like you, i did:
-Apexi cooler- i didnt feel much difference in power
-Full exaust- bit of difference, nothing impressive
-Splitfire coil pack- prob 2nd best mod, car went better and revved out much better without misfiring (in my case)
-turbotech 12psi- bit of difference not too bad.
-Mines comp-big diff.
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Now i was facing same question as you, and i did what 95% people would say NO to and i don't regret it one bit.
I needed a computer, or something like safc, full computer and i thought about the whole process, dyno tuning everytime and wiring bla bla so i decided to go for MINES computer.
Mines cuputer is a non tunable computer- its tuned to run on 12psi with basic mods (ones i already have).i Chose mines because i didnt want to go huge power, didnt want to go dyno tuning and installing and so on. I was happy to run 12psi on standard turbo just like you. And boy did it make HUGGEE difference. Before my 2nd would hardly churp, now i can do a burnout in 2nd, just to give you an idea. Befor emy 3rd and 4th, i would struggle with 5L and 5.7L holdens, now i beat 6Ls. Just to give you an idea of power gains. I know people are against Mines because its programmed to Jap conditions, but i would reccommend it to anyone.If you live close to me PM me and ill show ya thats if you ever wonder. No dyno needed, no wiring, just plug, and thats what i wanted.
Dangers-apparently leans out your engine, hasnt done it to mine?.
Hope my lil essay helped, good luck.