[fritz_t_coyote]

Wires were hard to pull off because the factory didn't use dielectric grease; Hopefully you DID use some with the new wires.

Modern engines (and plugs) go so long between changes that the boots will become one with the plug unless you use some dielectric grease inside the plug boot.

Likewise anti-seize on the plug threads.
Between the long change intervals, and the relatively soft aluminum cylinder head, Bad Things may happen at plug change time if you dont.