Removing relays and fuses to work around problems that are killing relays and fuses is a recipe for disaster if you ask me. I am all for reliable work arounds that are cheap and effective, but purposefully trying to melt wires and destroy electrical hardware is Darwinian. I know that helps you 0%, but people never cease to amaze me.
Why someone would run hotter plugs makes no sense either. I go to colder heats on our supercharged Miata to prevent detonation due to the hotter high pressure air. I would certainly replace the plugs with the appropriate heat.
Could be bad coil and/or CPS.
'06 XK Limited, 5.7L, QD II, Black, 163K
'02 WJ Overland, 4.7L HO, QD, Inferno Red, 126K