If you are going to run 1.2bar i would have a BPU upgrade done by a reputable garage, you would not be wise to just open up the hole in the restrictor ring as it gives you no control, the risk of the turbos going pop will be much higher at 1.2bar, how healthy is your engine (how many miles, service history, intercooler condition) what about fuel pump when was it last changed, fuel filter the same
Sorry to sound a bit negative but you really need to do these things properly if you want to avoid some of the risks, and yes I know how it feels to push a car too hard and loose an engine, its not funny or cheap:)