I have a complete jdm d15b vtec in my car right now, just picked up a nearly complete z6 and i'm looking to swap the z6 head over onto my d15b bottom end. as i understand, the d15b vtec is more of an economy mode vtec right? and the z6 head is more of an agressive head correct? how much power should i expect to gain (or lose)? I need to replace the head gasket on my d15 anyway, so it would be easy to throw on the z6 head when i replace it. Just wondering overall, which head would yield better power. thanks!