sorry but your talking out your arse, there are decent gains to be had with pretty basic head mods, which will yeild better drivability, and power... and by power that can mean the same power on less boost which is desirable a it means your doing less work /making less heat to make the power.
in terms of head work, you'll be looking at decreasing the compression anyway, so it makes sense to go over the head and do the basics not to mention the extra heat going in there, so personally I'd be looking at stainless valves.