I currently have 249.7kw @ 16psi, and I have some tips for you.
You will also need an upgraded clutch & flywheel. Budget about $1500.
You can save some money by looking for 2nd hand gear. I purchased 480cc S15 injectors for about $300 they are fine for 250rwkw, (I since sold them after finding my car already had Nismo 555's) my Z32 afm cost 120 delivered from the for sale section, my turbo was a 2nd hand hi flow (only done 200km before the bloke wrote the car off) for $1100 again from the for sale section.
And you can save money by doing stuff yourself. I put my turbo on it took some time but was not too difficult and saved me about $400, was going to do my injectors before i found them to be 555's would have saved me $250approx, wired up my Z32 myself, then took the car in for a tune. All of the steps above have good tutorials in the DIY section.