Here is a teaser for you Ants. A mate of mine took in a stock bottom end R34 with the same turbos as you, 270 somthing cams same ecu and at 18psi made 470hp at the wheels before our favorite timing jitter got in the way. It drives like a bloody stock one just with tonnes of balls! You may not experience the timing jitter just yet being a brand new engine and all. You could potentially go for 25psi and over 500hp at the wheels