The 2554r is a bit small on a ca18det. Adding 200cc to the engine is not going to help that much.
The restrictor is built in if you buy a real one new. I'd get the 2560r, there is a reason nissan chose that turbo: it works perfectly and shokes less at higher rpms. It will not overspin either.
As far as your other thread goes, you do not need a Z32 MAF (and it will require a retune, it wont work), so do not bother. I am running a 2560r on my ca18det at 15-20psi with an s14 SR20DET MAF and according to nistune it is not maxed. You are going to need bigger injectors before a bigger MAF anyway. If you go that route, get both at the same time as both require a remap.
Installing a FMIC is indeed a very good idea as the stock SMIC is so crap it can hardly cool the air compressed by the stock turbo at stock boost. It will quite nicely free up revs while cooling the charge. Basically it increases both reliability and power. Get one
