With diesels, more power is just a matter of adding more boost and increasing the maximum fueling rate.
How new is your car? Is the fuel delivery electronically or mechanically controlled?
To increase the boost don't adjust the actuator rod because you might go the wrong way and the wastegate might leak. Use a
boost controller instead and this makes it easier to adjust the boost. Also fit a
boost gauge so that you have an idea for how much boost you have.
From there you just have to increase the fueling, otherwise there will be no power gain with just more air...
Removing as much of the restrictive stuff on the intake side as you can is a good idea. Getting a K&N panel or pod filter will improve performance, especially when you have more airflow with increased boost. Removing the cat is bad for the environment! Getting a bigger, high-flow cat converter as well as a bigger diameter exhaust and dump pipe will help with performance too. If the engine doesn't have an intercooler, fit one, otherwise fit a bigger one if it already has one. The intercooler will help to reduce the engine intake air temps with the increase in boost.
Ideally, a bigger turbo sized to the power you want to get should be fitted for the best performance but that, along with intercooler and exhaust starts to add up pretty fast and you may not want to spend that much money. I imagine the standard turbo give about 6 or 7 psi of boost for 80hp. if you wanted 150hp, you'd need a turbo that is ideally suited to deliver the sort of flow rate for that power figure at about 15 psi of boost. Or for 200hp, you'll need 27psi of boost and something around 20 lb/min of airflow (and a huge intercooler to keep the temps down because intake temps will be up towards 100 degrees at that boost level!).
As far as I know, there are still no off the shelf Getz performance dampers. That said, you can still piece together a good kit as a few others and I have done on this forum. Its a mix of Koni parts. If you're interested PM me and I will see if I still have the info around somewhere. Otherwise if you're into spending lots, then there are a few good coilover kits available. Fitting eccentric upper clevis bolts to your front struts/hubs give you a bit of adjustment to dial you camber in a few degrees too.
Finally, I dont know how any of this will help you with smog/registration/etc so just have to be careful what you start swapping out...