First let me say NGKs are my plug of choice in my Harley as well but I see a lot of people were posting that one plug cooler as being an incorrect plug. It may not be oem but running a cooler plug is often beneficial. Especially in today's world of emissions mandates wanting every last drop and then some burned. The tendency by manufacturers is to run as hot a plug as possible to meet these standards. Running a cooler one can reduce heat and unless plugs are fouling, I run one cooler.
The other thing I see is people using antisieze on them. Totally unnecessary with NGKs. They have a special coating already. One of the things I like about them. I've never used antisieze with NGKs.
Lubricants can also alter torque values by as much as 20% which in the case of spark plugs can can issues of another nature.
Forgive me if these issues have been discussed/corrected in subsequent threads I haven't seen. Just something I noticed in spark plug threads I've been reading.
Directly from NGK...

"For spark plugs with special metal plating simply do not use anti-seize on initial
Installation; All NGK Spark Plugs are manufactured with a special trivalent Zinc-chromate shell plating
that is designed to prevent both corrosion and seizure to the cylinder head; Thus eliminating the need
for any thread compounds or lubricants."

 

Unfortunately the site Search has taken a siesta since a site update a couple years ago. I can't even find some posts of my own with the exact title.

But that insert from NGK is a knowledge nugget...TY. There are new tipped plugs out there with ruthenium on them (attached PDF).
Updates are always nice, our cars are hitting their 20's and that's antique tech. Anything to enrich these girls lives is welcome as far as I'm concerned.

 

I've posted NGKs position NOT to add anti-seize with NGKs multiple times.