hi oz gtr,get yourself a new tuner.
heres an example.
r32gtr
trust cooler,16psi,standard computer,exhaust,airfilters.
231 kw rear wheels.ran 11.8 at 121mph
i had similar on a r33gtr with power fc,made 255kw@4.
on 2 different dyno dynamics dyno.one was 255kw other was 251kw.
after being sold was redynoed on different dyno by new owner and made 254kw.