@mickd on more modified engines the combustion chamber can heat to beyond optimal temperature so using a cooler plug will reduce the combustion temp, changing plugs to a cooler type when not necessary though will only foul plugs.
An ECU tune isn't going to be anywhere near the level required to even think about using cooler plugs, using hotter fuel is a common reason for changing plugs but again I doubt the OP will be running race fuel as the engine would require much more modifications to do so.
@CraigB Yeah, couldn't agree more with what you're saying.
Think OP was listening to a tuning company or similar, basically a "money vampire doing hand relief ", just stroking the ego.
Even if multiple mech components are changed and you score an extra 100 hp
(
), a commuter racer can't be operating at that range long enough to warrant diff plugs. If a track day is on the cards, go for sticky rubber and brake late .