I'm running a VF28 which is basically the same as a VF30/35 and it's pretty much maxed at 335BHP (1.5bar peak, 1.3bar at top end). I may be able to get it to 350, but then I would be mapping beyond safe and efficient limits. I also have all the gear in the car to monitor health at all times, so could spot any issues which (no offence intended) jo public would not have visibility of.
To get between 350-400BHP you need an STi for starters
or at least a good forged WRX short engine.
Then bolt on a MD321H/T or a genuine 18G or 20G.
To get 380BHP from a WRX block is very very optimistic, and will also shorten your gearbox life considerably.
You'd be suprised how good 320-340BHP feels in a WRX, as it's still a huge jump from the stock 218BHP (ish) figure.