67 twin turbo dart

I order NGK plugs from Rock Auto in bulk. The colder ones will be more likely to fuel foul if the tune is fat. I run a 6 heat range on the street and 8 at the track. I just got some 5s to try this year with 87 octane.
Yeah its the 8s, tune is rough but he kept the afrs 11.5. I'll get some more cooper ones to use and test