Who's running NGK ZFR5N in there Slant?

I will add that in those days, in the shop, we saw an unusually high amount of plug fouling with Champs. We were sourcing from pro-suppliers, so, they weren't discount specials. I have no evidence to support this, but the parts supplier reps were telling Us there was a change in production & the heat ranges were too cold/inconsistant, take that for what it is...anecdotal heresay....but that was the "buzz" at the time.