^^^what he said...you need the tune before you can start thrashing it...or even driving it really. Have you got bigger injectors, fuel pump, and an aftermarket ecu or nistune chip?
Dunno if you have already done this but get your car up to 100 or so in third gear - downhill would be better but not necessary - and then take your foot off the gas for five to eight seconds and then floor it. Do you get a cloud of smoke out the back and if so what colour is it?
Plazmaman is about $1700, genuine Greddy $1300 or more, Freddy about $300 or OEM replacement from wreckers under $100. I doubt you would feel the difference between any of them.
Def OEM throttle body will be fine - so will OEM manifold.
Have you already got a big turbo, injectors, FMIC, exhaust, aftermarket ecu? These all help to make the car go faster. A FFP will not.
Yes and yes. Get yours cleaned and tested or
https://www.trademe.co.nz/motors/car-parts-accessories/nissan/engines/listing-2011817312.htm?rsqid=7882f898254d43ba861b09f968045caf
(was $80 for 6 including rail).
Well GCG say 400 to 600 bhp which is a pretty big range but how much you can make depends on lots of variables including choice of supporting bits and quality of tune. The thread that Ravi pointed you to will give you some ideas.
Its a catch can unless its some how baffled at least. Read all of the thread - you will find that the vast quantity of oil requires more than a simple solution in this case - otherwise you are just pouring oil into the turbo intake.
Your tuner sounds weird. Your car is losing power when hot? So you put your car on the dyno and it makes X bhp and when it warms up it makes x -30 bhp? Is he saying it is overheating?
Water/methanol injection is a whole other subject but no you won't need anti-freeze. Methanol is an effective anti-freeze....
Go down to the Forced Induction section and click on the RB25 turbo upgrade results and see what other people have done. Start at the end rather than in the distant years of the beginning.
OEM or Splitfire. There are other acceptable options but they require a little more work. Try gapping your plugs (if they look new - otherwise replace them as per above) to 0.8mm first.
Turn up the boost!
Would have thought you replaced the plugs when you did the coils. What sort of coils are they? Many dodgy ones out there.
Plugs NGK BCPR7ES (copper) or better PFR7G-11S
Try a smaller gap 0.8mm