Power costs money - no way round that. GT3540 is too big. .. and there is a big difference between 200kw and 250!
If you don't have bags of cash (who does?) then get a fmic, 3in turbo back exhaust, a Nistune chip for your ecu turn your boost up to 12 psi and get it tuned - that will give you a noticeable increase in zip.
Then save up for a Hypergear turbo which will slot right in without fabricating new lines etc, a z32 afm and bigger injectors... and then another tune.