I hope that i m not too late:)
In my openion in NA tuning v use the inertial of the intake charge to fill in more n more air n thats y v need bigger cams n also needs to go high on the rpms.
the valve curtain area is a criticle thing in order to judge how good a head is volumetrically. The valve lift n dia dictates the max flow capacity of the valve under a given atmo presure.
the duration is related to the degrees of the crank shaft. If there is more inertia in the intake charge then a bigger cam can be used to get more air pumped into the cylender.
the stroke, the port cross sectional area, the valve LD ratio, the cam lobe centre, the runner lenght, the Rpms, all help is calculating the speed of intake charge. which in return helps in calculating the CFM consumed through the help of converting the velocity of the charge from a specified cross sectional area, into CFM. N the CFMs tells how much power can be generated at a specific rpms.
An increase in static compression ratio use the combustion energy more effeciently.
A reduction in the weight of any moving parts would help reduce the inertial load of the parts,e.g, flywheel, pistons, rods.
Reducing the back presure while using the scavenging effect would defenitly help the engine to breath more effeciently.