Wax it
Everybody who gets these cars seems to want to make it faster before anything else and with them so easy to modify it's simple to do.
Sticking the CT9 route you will want a FMIC, FPR, Adjustable actuator, decat, manifold, FCD, full exhaust system, air filter relocation, aircon removed, boost controller and a boost gauge check the pressure. All those in place? Take it to tuners and set it up to a bar and it should make around 160-190bhp for an estimate. For a bit more money look at a hybrid CT9 to get a nice solid 200BHP with a good tune.
If you want more power, stick a TD04 on it with an uprated fuel pump, maybe new injectors 330cc and think about adding an aftermarket ECU (e-manage, Dastek etc) then take it to a tuners and get it setup.
Quite possibly missed something but that's a few tips on how to get more power. Just remember to insure all the modifications you do because one crash, check over by VOSA or a mate pissed that you can get to 60 faster than him and your fucked.