According to wikipedia
"At the heart of the R is a newly developed version of the four-cylinder 2.0-litre turbocharged EA888 TSI petrol engine used in the latest Golf GTI, but in this application producing 300 PS from 5,500 to 6,200 rpm and 380 Nm (280 lbs ft) from 1,800 to 5,500 rpm. Compared with the GTI’s powerplant, the Golf R’s engine has a modified cylinder head, exhaust valves, valve seats and springs, pistons, injection valves and turbocharger"