it's diffrently build than a regular sr20de head. Think of it, they made up to 340 BHP as a 2.0 natural aspiration engine, try to make that with a a stock SR20de head!
its a bit different built up and the ports are about twice the size areal or a sr20de head + valves guides and such is not regular. Flows unbelivable good, and when youhit up a turbo on this there is crazyness happening, could not done the same with a normal sr20de head at all.
+ there was made about 34 of them, and I heard there is about 12 left, which makes it pretty special itself. it's a lot of tech inside, ofc on the outside it looks normal, it isnt always the outside look that tells you everything you know
the BTCC engines and heads were produced by Janspeed UK on licence from Nissan. At first Tomei was chosen to make this but they failed so Janspeed took over