spark plug heat range questions.

and there is now way the engine could possibly be running better because of the 1 step colder spark plug?
I went from ngk v-power zfr5f11's to autolite 3923's.
I swear it pulls a little harder when first dabbing into the throttle from a steady cruise. since i run 91 octane fuel and run 14 degrees of initial timing isnt it safe to say a 1 step colder spark plug would be a benefit compared to running the stock heat range?
And if it doesnt help anything then why do half the people who run magnum v-8's buy the 1 step colder plugs? to help with engine ping, When your engine isnt pinging then im sure its safe to say its running more efficiently and there fore getting better fuel mileage and performin better correct?
I know they said high altitude calls for a warmer plug, i live 4000 feet above sea level, but i run 91 octane fuel and 14 degrees of initial timing, even thinking about turning it up from 14 degrees initial to 16 degrees initial. Wich would make my total timing go up from 32 to 34. Is the magnum engine going to run better at 32 degrees total or 34 degrees total?