mac ,I've noticed with IR (NGK endure better than Denso) in three vehicles , two of which had adj. base timing and in AZ summer w/ 103 +Deg, F (103 -119 deg
) Hottest days would ping (always prem.gas used) much , much less using Irridium and even could adv. timing that 1 to 2 degrees like when it's COOL for retaining awsome RESPONSE .
Difference admittedly minor ,but we all try to do things that all ADD-UP collectively to gain performance ! Like guys putting something that costs several HUNDRED $$$$$ and get 18 more HP (over narrow rpm spectrum )