An automotive vehicle engine includes multiple power-producing cylinders including a first group of deactivation cylinders capable of being selectively deactivated during engine operation and a second group of cylinders capable of continued power production during deactivation of the first group. An air intake system includes a turbocharger compressor connected to intake valves of all the cylinders for supplying charge air to the cylinders. An exhaust system includes a turbine connected for driving the compressor, which includes twin scrolls with first and second exhaust flow passages separately connecting the turbine with exhaust valves of the first group of cylinders and with exhaust valves of the second group of cylinders. At high loads, the engine operates on all cylinders and is turbocharged for maximum power. At lower loads, the first group of cylinders may be deactivated and the engine may be driven by the second group of cylinders to obtain increased fuel efficiency.