Is there any benefit from upgrade a 06 head to a 08 head? I know the intake tract was straightened, what kind of changes in power could be expected from that? I know the '08's were up a couple HP from the '06, where did this extra power come from? Is one better than the other to use as a base to get a professional port job done? Any information anyone has on differences between these two would be appreciated, I am at a spot where I may need to purchase a new head and am looking for more mid-top performance vs. my stock ported '06 head. Thank you.