Yeah the shape is a bit more hard edged than normal legacy shapes have been.
As for parts I have used and run on mine:
BOV: Have had GFB respons on mine. Was nice to be able to make noise or none at all. I added it though to stop the factory uint from leaking they are know to be very bad a leaking especially it boost starts to go above 13/14 psi is leaks away and the turbo has to work its ass off to try and keep levels where they should be. (so can be a good mod if your one is leaking, However downside to this is.... If you have a exhaust that now flows better along with this and possibly an intake you will get boost spikes and boost cut without a tune.)
Exhaust: I went for HKS Premium ES system after talking to @sobanoodle, He had tried others and found them to sound bad or drone like crazy. This one gives you a nice sound with out stupid drone inside. This is my BR9 with before and after of the exhaust
Intake: Have used HKS intake system from turbo to intercooler and filter to turbo. If the car is NZ new the turbo to intercooler wont fit from what i understand.
Brakes: @sobanoodle did alot of work on this suggest you have a look at his posts about these.
Big changes in handling come from Bracing and sway bar upgrades in this chassis, I have cusco rear and front bracing as well as Whiteline sway bar that has really changed how this car handles around corners now. Its a heavy car but sits much flatter and has more control in the steering inputs.
Mine came with STi lowering springs from factory, however there are lowering spring options you can get or of course go full coilover and be able to dial it to what ever you like.
If you do the exhaust and even an intake take and get it tuned, I had planned on SAS doing mine here but work has got rid of me so need to hold that off. If you up north hit up Possum Borne Motorsport they can sort you out with all the tune and parts.
Any more Q feel free to PM