Exhaust - $200 - secondhand 3" catback
Intake - K&N panel in factory box - ~$100, alternatively if you want a pod filter get an apexi power intake for around $80, but you will need to fabricate a partition and CAI
Intercooler upgrade - $200+ - That price would be for a secondhand R34 sidemount cooler. If you want a front mount then a generic kit can be had for around $400 - 500
Boost Increase - Get a $30 turbotech bleed valve and be done with it. There is no point spending $400+ for an EBC with the power you are chasing.
Realistically there are a few other things you need to make 200rwkw. Firstly ,as a safeguard, I would replace the tired old factory fuel pump with either a Walboro or a Bosch 040, both can be had for around $200
You WILL need some sort of engine management, but for your target power level an apexi SAFC should be fine, cost around $300 secondhand