What spark plugs?

heat range, too cold-it can't clean itself and fouls,
too hot- can cause pre ignition from the plugs 'excessive heat' preigniting the fuel before spark even happens.
it's a cleaning thing.jmo

and heat range does not change the mixture, it just fools some tuners into thinking it does by either being too cold and showing rich/fouling or too hot and cleaning itself of any mix trace giving the impression of lean. jmo

the timing is shown on the strap, it being clean makes no diff to me, it's the white shadow marks left from the total & initial timing, the total being way down the tang almost to the base ring shows a lot of total while the upper portion shows initial which is a lil low but not bad.jmo