I don't know how this would play into a turbo application,but the gsr head is going to have secondary runners on the intake and the B16 head won't. I have seen some guys on teamintegra.com talking about disabling the secondary runners so maybe they are not as good as the regular B16 runners. Just a thought, maybe someone will correct anything that is not true or explain why or why not the secondary runners will help or hurt the performance from a turbo motor.