with your current mods, your max power will be around 180kw (no exhaust mentioned). splitfires wont be needed.
edit: just get some decent spark plugs, part no: BCPR6ES, then gap them down to .8mm or lower.
i'd definitely look into getting a turbo back exhaust to push your possible power to 200kw. you wont need a decat (illegal in most states and is a hefty fine if you get busted).
so, what you'd get before the tune:
-fuel pump (040, 044, walbro or nismo)
-exhaust:
get a split dump pipe, or a split dump/front pipe in 1. hiflow cat. and any 3" cat back exhaust you like.
-you wont need a fuel reg.
turbo elbow isnt an aftermarket item. its a standard feature on your standard turbo
downpipe = dump pipe (already mentioned).
hit the Queensland section of the site and do a search.
i'd keep the boost standard till you get an exhaust. you'll usually gain around 3psi from a nice flowing exhaust. if you turn the boost up to 12psi now, then get an exhaust you'll run 15psi without noticing. so just install the boost controller, leave it at around 9-10psi and get the exhaust installed. if you hit above 12psi then you'd want to turn it back. i wouldnt run 12psi constantly on the standard turbo either.