HT/Spark Plug leads

Hi folks,

a while back i had an AA call out while ironically dropping my dad off to get his motor back from some repairs. Cylinder 3 was misfiring and AA just replaced the no. 3 lead with one the fella had in the van. It was way too long and annoyed me being messy 😛 long story short, the other day I thought I’d noticed a couple of misses, nothing drastic but eyebrow raising. Bought some new leads (NKG) and replaced - running smooth as butter now. I noticed the number four lead (the one annoying one behind the turbo heat shield) had burned through the outermost layer of insulation. 
 

Seen a few threads saying the original leads were more prone to this than new ones. 
 

was surprised at the fact the engine seemed to be running much smoother after replacing too. Might be something to think about if folks are notice the odd grumble. 
 

bonus photo in front of morecambe bay freshly polished (just seen i missed cleaning a wheel though 😂)