i want to know which head to use and why? Is the Y8 OBD-2? Which is the least pain? Also i hear the Y8 has much more comp than the z6? but which head would be a more relaible setup? Can you also tell me something about the Si cable tranny? I have a D15B2 block that i would be putting th head on so i need a reliable but strong setup? Also i see the redline for my block is 6k and the heads are both 6600 so what can i do to get the block to handle the rev up to say 7k because i plan on building the head and the block. Thanks for the help i searched and searched so i hope i dont **** anyone off asking these questions over and over. Thanx