A method for controlling a turbocharger system fluidly connected to an exhaust manifold of a combustion engine and an exhaust after treatment system , said turbocharger system comprising a turbocharger turbine operable by exhaust gases from said exhaust manifold, and a tank with pressurized gas, said tank being fluidly connectable to said turbocharger turbine, wherein said combustion engine is operable in a plurality of engine operational modes, including a low NOx mode in which the combustion engine is operated in order to reduce the NOx emissions, wherein injection of pressurized gas from said tank when the combustion engine is in said low NOx mode enables compensation for an impaired engine performance parameter in the form of impaired torque response, said method comprising the steps of: determining a NOx parameter being indicative of, or correlated to, NOx emissions from said exhaust after treatment system; injecting pressurized gas from said tank to drive said turbocharger turbine based on the determined NOx parameter, wherein a determined NOx parameter above a pre-defined first threshold determines that pressurized gas from said tank is injected, and a determined NOx parameter below said pre-defined first threshold determines that the injection functionality of pressurized gas is deactivated, wherein - the NOx parameter is the NOx concentration in the exhaust after treatment system, the method comprising the step of measuring NOx emissions using a NOx measuring device arranged in said exhaust after treatment system. wherein said combustion engine is operable in a plurality of engine operational modes, including a low NOx mode in which the combustion engine is operated in order to reduce the NOx emissions, wherein injection of pressurized gas from said tank when the combustion engine is in said low NOx mode enables compensation for an impaired engine performance parameter in the form of impaired torque response, said method comprising the steps of: determining a NOx parameter being indicative of, or correlated to, NOx emissions from said exhaust after treatment system; injecting pressurized gas from said tank to drive said turbocharger turbine based on the determined NOx parameter, wherein a determined NOx parameter above a pre-defined first threshold determines that pressurized gas from said tank is injected, and a determined NOx parameter below said pre-defined first threshold determines that the injection functionality of pressurized gas is deactivated, wherein - the NOx parameter is the NOx concentration in the exhaust after treatment system, the method comprising the step of measuring NOx emissions using a NOx measuring device arranged in said exhaust after treatment system. determining a NOx parameter being indicative of, or correlated to, NOx emissions from said exhaust after treatment system; injecting pressurized gas from said tank to drive said turbocharger turbine based on the determined NOx parameter, wherein a determined NOx parameter above a pre-defined first threshold determines that pressurized gas from said tank is injected, and a determined NOx parameter below said pre-defined first threshold determines that the injection functionality of pressurized gas is deactivated, wherein - the NOx parameter is the NOx concentration in the exhaust after treatment system, the method comprising the step of measuring NOx emissions using a NOx measuring device arranged in said exhaust after treatment system. - the NOx parameter is the NOx concentration in the exhaust after treatment system, the method comprising the step of measuring NOx emissions using a NOx measuring device arranged in said exhaust after treatment system. <EOS>