I have read that are people in uk have soon more 600 bhp+ and some even 700 bhp or more in their gtir.
The can make very good track or dragstrip cars when setup and tuned right but a gti-r needs a gearbox whit a longer fith gear to make the most of the engine the fastest gtir's are only good for something like 160 mph topspeed because of the short gearing of the gearbox.