Harri Arola races a Subaru Impreza built by Valtonen Motorsport in Finnish Rallycross and Rallysprint. Under the hood sits a turbocharged SR20DET inline-four that makes 550-580 horsepower and 750-800 Nm (553-590 lb-ft) of torque with a 45 mm restrictor. The engine features a Holset HX35 turbocharger, Haltech ECU, and runs on E98 fuel. The car still retains 4WD however not with Subaru parts. A Nissan GTR five-speed transmission converted to sequential straight-cut gearset by PGS Transmissions sends power to GTR differentials front and back.
Source: Arola Racing FB page and Valtonen Motorsport FB page via Stav-Tech