it all depends, a B16 is very very similar to the ITR in ways of design, shape, volume, and flow, they are almost identical.

the gsR is slightly different from both of them, it will yield you more power directly after the swap because the gsR yields higher compression. but i have always heard of people saying they dont flow as much.

there is of course contradicting sites with different flow numbers for both of the heads, anywhere from RLS,portflow,alaniz,JG


hope this helps