280kw = 375whp. Thats more than mine makes with all my list of mods at 1.3bar. You ran 1.2bar/17-18psi on stock turbos? Where did you get yours dyno'd?
Say if you do a turbo-back exhaust (de-cat), pod filters, boost the turbo's a few pounds higher than factory and install a power-fc, how much awhp should if expect within reason on a safe tune?
Syfon: Rohans GTR has catback only, pods pfc and running 14psi (1bar) - made 240awhp on that 40deg day at autoworx a while back where everyone elses' numbers were hammered.