My mate Peter just had the poverty 257 engine I assembled for him in the ACT tuned at ESP racing. I built this engine 2 years ago.
It made 246 kW and 550 nm at 22psi tapering to 18 psi at higher boost.
It's a bits a engine made from assorted left over 08 sti parts from 257 engines with just a set of CP pistons and a set of head studs. I blocked off the avcs and plugged up the oil holes in the cams and made a cam trigger bracket for the head to suit a set of 99/00 cam wheels. Running vipec
ecu. On 98 Ron fuel Peter tells me he has the same turbo as you are running