Sorry. I had to go before finishing my reply. The ceramic turbos are built for reliability but most of us want boost
Different people saying different boost levels are safe (about 1.0 bar max). If you want to run more power by running more boost, get the turbos swapped for some with the steel inners. I would have thought that you can run as much boost as you like but then the injectors will not be big enough and the turbos can only flow so much air. I run 1.1 bar, could run 1.2 bar with ignition retarded and could really run 1.4 bar but would be maxxing out injectors so leave it as it is.
Unless you like DIY, pick your favourite tuner, give them a ring and ask for advice. No idea about the price though, mine came ready to rumble
Hope that helps.