A lot of my slower NA friends where cracking their NGK plugs last winter. We figured it was a bad production run.
If o2bncamo is right, detonation can be very expensive. If it is detonation you need to get it fixed quick.
I add 10% race gas as cheap insurance.
I did have detonation once after I started adding race gas . It was at the start of a day when I would get into the throttle. It cleared up after a while and I the rest of the day it was fine.
Thanks for the response. We have it narrowed down to a few different things. This season we will be trying a low compression head to help bring the octane level needed down a little. I guess time will tell.