I am ashamed to say it took me a few days to spot this thread
So Hi
I am currently six years into finding out what can be done to a stagea , ( the answer is quite a lot )
If you have a stock car the general consensus is to do thinks in the following order
Uprate the brakes first Like most nissans RS Four Brakes are crap - 32/3/4 GTR will do (for now
)
Complete exhaust decat and induction
Do the manual conversion early certainly and definately before you tune it or you will be buying bits twice as the type of box determines which ECU you need
Link G4s are excellent and will do everything you need and more . I have one on my car and it is the dogs. Incedently if you do need one I can get a discount off the list price as I doubt you will find a second hand one.
Exhaust manifolds wont give you much gain as the RB manifolds perform pretty well but the stock ones on RB25s do break bolts so a sensible mod.
Changing the arms is worthwhile but changing the main subframe bushes gives the most improvement as these bushes are rarely changed and nealy always shagged (please excuse the use of highly technical jargon ).
You dont want to lock it with steel collars or solid bushes. I fitted whiteline polybushes which made a huge difference , They are also a lot less than half the cost of the oem nissan jobbies and you can get them in the ulk
Suspension 33 gts/gtr wont fit you need stagea specific bits Im afraid. But the rest of the set up (arms etc ) is interchangeable with GTR.
You can fit GTR suspension but this needs some other changes . Ive filled up your thread enough already so will stop now,.
but if you want that info (and more) I will be glad to help.
Nor really up on tuning RB25s as I have an RB28 in mine but anything that works for a GTS works for a stagea (once it has the manual box in )
Hope this helps