spoke with an engineer today about the heads and they are different, the california heads do not flow as well vs the non egr ones he said the valve seats are not the same and something to do with the casting too but he was not exactly sure, so if you have a truck equipped with the egr your have more to overcome then just the egr valve, this is good and bad as it means i have one of the quickest emission trucks around but i am playing against a stacked deck competing with non egr trucks. looks like i am going to have to find some new heads to go with the upcoming turbo.

I work at GM and we are preparing to take over casting the new dmax blocks(not the heads) I do get some good info here and there.