Ok lets try this again. If you go to a bigger valve size and to not touch the port its a waste of money. It would be like peeing into a bigger funnel with the same outlet. bigger valve take a bigger throat. Throat size is APPROXIMATELY 89-91% of the intake valve size, slightly bigger on the exhaust. This increases the velocity speed at the venturi. Sizing must be done to see gains. To little no gain, get greedy and you TRASH the head. As far as turbulence that is mostly cured by poor shaping and lack of required area and should be addressed. 28 inches of depression is the industry standard but last I've heard nobody is sure exactly how high the depression is in a running race engine but it is suspected to be MUCH higher.