Road tuning by my engine builder and Haltech tuner showed problems with the boost control. He suggested to change to the strong 1.2bar actuator, didn't help, suggested to change to the Turbosmart IWG-75 dual port actuator, didn't help again. He suspects a clogged or otherwise to restrictive catalyst converter but I hadn't had the time to get it on a lift to check that.
It reached 1.8 bar @4000rpm but quickly fell off to about 1.2bar.
Still enough to close in on a Porsche Cayman GT4, overtake it and outrun it at 275+ km/h.
The goal is still to reach 300km/h.