Hey everybody, whats the next mod i should do to my GTR? right now it has HKS exhaust, downpipe, turbo timer, Blitz boost controller, ADR EPROM, Koyo rad.[/quote]
Id suggest buying an Greddy intake hardpipe kit or upgrading to BNR34 N1 turbos. Or some other ideas would be to through in a set of Tomei PONCAMS or adjustable sprockets.
Get a clutch so you can launch it, the stock clutches are useless when you start to mod gtr’s! After that, there’s a big list of stuff that can be done, hardpipe kit, steel wheeled turbo’s so they dont blow, aftermarket intercooler, oil cooler and relocation kit, cams as adam mentioned, bigger injectors are also needed if you want to utilize bigger turbo’s. Id also investigate a full motor rebuild. Higher mileage GTR’s sure like to explode when modded if you have stock oil pump drive on the crank, and the #6 cylinders tend to go as well. I personally wouldnt go too boost happy with a 100 000km+ rb26, and if you do, make sure your getting enough fuel in there so you dont melt the #6. I didnt know that car had downpipe, koyo rad, and ADR eprom though…cool… 
First, consider your objectives. If you can stay happy with, say, 300 whp you probably don’t have to worry too much about your aging engine until it tells you it’s time for a rebuild. If you want to go after much more power, you’ve got establish a solid base to build on. This means rebuild, and, while you’re at it, pistons and rods to match your plans.
If you don’t want to spend that money now, focus on efficiency-based mods that will help your engine make all the power it can without shortening its life a whole bunch. Intake is at the top of this list given that you’ve got an exhaust. Don’t get to greedy with boost or you will pay! (See paragraph 1)
I’d buy the Apexi Power intake. Best filtration AND best power of half a dozen aftermarket filters. Hard to argue with that. You’ll get more out of your intake if you make sure it gets lots of cool outside air rather than sucking from the inferno your engine lives in!
What’s an ADR EPROM? Are you programming your ECU?
If you’re going to start playing with tuning, I’d suggest a wideband O2 for keeping track of A/F mixture and dual channel EGTs to make sure you’re not burning too hot.
Better to know the effect of your tuning tweaks before they turn around and bite you!
Have fun!
Dan
really good advise
justin, we need to know your goals to offer advice.