Very nice car there buddy! Hope to see it at a cruise, event, etc.
Upgrade brakes (min.: gtr brembos with slotted rotors, decent pads, and motul RBF600 brake fluid), coil-overs, sway bars, bushes, etc.
You have plenty of power, but it is useless without the tools that puts the power to the ground reliably.
If you have two cars and the same budget:
Car 1 gets the engine, power, ecu mods
Car 2 gets the braking, handling, ecu mods
- Car 2 will always be quicker (and safer) on the track and on the streets.
Don't mean to sound like an asshole, as the work has been very well done and the car looks awesome, but you need to consider spending money on handling b4 getting more power.
I thrilled mates that have 400+rwkw skylines with my 250rwkw line as my braking and handling is ALOT better.