Hi and welcome to SES
Car looks nice, and sensible mods.
As above - Duncan @ Racedynamix is used by peeps on here, as well as Rich @ FB Tuning (see my signature for details).
Charlie down at Surrey Rolling Road is most peoples choice for a Dyno - handy as Duncan Maps there as well.
260-270bhp sounds about right for the mods you are running.
To get any more you will need a turbo from an STi (VF35 or the like), probably STi 565cc pink injectors, and maybe an STi top mount. That along with a new map from Duncan or Rich, should see you 330bhp ish
Ryan