I've been running the 7EIX (per a different thread here somewhere) with no problems and it looks clean when I check it. Maybe I'll try the 8EIX in Mrs. 2LZ RX3 and see if there's any real running or carbon difference between the two......
I really don't think there's a ton to be concerned about in just one step in heat range.

I saw .75mm gap on the 7EIX on a previous page but do we have a consensus on that?

What gap is everyone running the NGK Iridium plug at in your RX3???? I thought it came out of the box kind of wide.

Guess I should have looked here first.
Looks like .031" or 8mm.

https://www.ngk.com/product.aspx?zpid=9663