Quickest way to go:
-Walboro fuel pump (255lph),
-600-750cc injectors or more,
any newer sti varient turbo (vf39/43/48 or the japanese varients you guys can easily get a hold of)
(I'd get rid of your catted uppipe as well so you don't grenade the turbo with catylitic converter pieced)
That's the minimum really to get around that ballpark of 250. More parts would make the job a little better but are simply icing on the cake. i.e. 3 port boost controller, full exhaust, intake, inlet etc...
For 190-200kw you'd really only need to swap turbos and downpipe and retune.
so 200-250 kW is about 270-335 hp. The basic VF turbo route can get you 275 to 300 whp, relatively safely and easily. To get to closer to 335 whp would be more like an 18G size turbo. The VF is about as large as you would want to run with stock injectors, if that factors into things. Go larger than a VF and you also increase the likelihood of busting a piston and needing a complete engine rebuild.