Turn your canooter valve up all the way and plug off the Fallopian tube Sent from my iPhone using Tapatalk
That just keeps things running smoothly, nothing more. Only way to get gains is to build the motor or T/C that little sucker.
Well, you MIGHT gain something, but that means that you were losing performance with the old wires. Replacing good stock wires with good new NGKs gains nothing, except maybe a longer expected service life before you have to do it again. I suppose that adequately upgraded plug wires might allow you to use a higher energy ignition system if there were also a lot of other modifications done which would require that you use upgraded spark plug wires in order for them to be useful, but if you're doing that, you aren't asking this question.
Probably not. But, I consider it part of a full tune up (add a cap and rotor), which won't hurt the car 1 bit, and may make it run better.