GTiR ITB's does not even fit a bit to the head, Had to fabricate to make it work, and tons of porting of the ITB's to make them work.
Here is a picture of a original/stock BTCC engine
Ports are twice as large as any normal SR head, Janspeed/ Nissan spent 36 million GBP back in the 90s to make the engine for the BTCC cars produced upto 340 BHP naturally aspired as a 2.0