I run the NGK BKR6E in my 505 , same plug in my 440 . 505 is 11:1.
Never any issues . Under 10:1 NA I would run -5
These are projected plugs.
Only thing with NGK's is they hate being over fuelled .
Tex
That's good info and I like the fact that you race it and get real world tested info which is helpful for some of us in a similar scenario.......Dyno stuff for sure has it's place especially a chassis dyno in a real world load zone simulating going down the street or track but, I still have tried adding more fuel, timing air pressure and launch/suspension settings to get more out of my car and a few others along the way............