ok maybe i'll try to be a bit more helpful heheh.. lets see if we can work out what it is you need for 400rwhp.. no flaming ah, only trying to help ;)
1) exhaust - 3" to 3.5"you choose how big you want it to be but general rule of thumb is 3" and above, mine was a 3" dump which ended in a 3.25" catback exhaust.. you can go Jap brand or do a custom job but expect costs to vary somewhat..
2) filter - pod filter or high flow panel filter.. most go for pod cause it sounds better.. i used Apexi, dont use HKS unless you only wanna filter out small birds..
3) turbo - no way the stock turbo will make anything close to 400rwhp so you would need a new one.. HKS turbos that fit your application are the 2835 which has several versions from 380 to 420 and the 3037 which has 420 to 470hp variants.. there are other brands you can use Apexi, Greddy etc but ive had experience with HKS and i like them a lot.. the choice is yours tho
4) fuel system - fuel pump, maybe a Bosch or a Nismo.. i dont think the Walbro that most ppl use will support 400rwhp safely.. might also need a new set of injectors.. 550 should be more than adequate but if you're going to go for more power than maybe buy bigger ones in advance :)
5) cooling system - you will need a front mount intercooler, the stock cooler on the 34, though thicker than on the 33 is good enough if your car is stock, but 400rwhp requires a better cooler.. again, you can choose between the Jap brands or just get a core and do up the piping yourself
6) ECU - well, this is a huge topic in itself.. what do you wanna go for? piggyback or standalone? if you want piggy back you can go for SAFC + ITC or E-Manage or F-COn.. depends on your budget.. if you want a standalone, then you can pick PowerFC, MOTEC, Microtech, Haltech and more.. Power-FC is good coz its PnP so no messing around with wiring, just plug it in and you can drive it with the base map tho thats tuned for Jap fuel.. but no problems, it should be good enough to drive to the tuner and get it sorted.. however, best bet is to pick a good tuner coz if your tuner isnt good at tuning that ECU then its all wasted..
7) suspension and brakes - often neglected by people, id rather have a car with 300rwhp and good handling than a 400rwhp car that drives like the Titanic.. these mods will keep you on the road and stop better esp when your talking abt 80-100% increases in output.. coilover *may* be too hard for your liking esp with Msian roads being what they are.. i used Bilstein before and then moved on to RG coilovers.. the RG suspension is superb, take corners at high speeds and the car is so stable its not funny but the Bilstein was nicer around town, no harsh ride.. moving onto brakes, maybe just upgraded rotors and better brake pads will suffice for the mean time.. if you have the cash then hey, by all means go for Brembo or Alcon or AP Racing etc but you wont get that and all the above for 10k
Happy modding dude, i know the excitement of owning a new car and i hope you enjoy your new ride.. I may have left out 1-2 items in the list so i'll edit it when i remember hahaha.. but i'm sure the sifu's here will add to it soon