The ST gs40 came with a plug, was using that

I first benched the engine on 15% glow and got an offpeak tune of 14k to compare tests to.
I then guessed a half turn richer as a starting point for the 5:1 E85Castor
(if I was gonna be wrong, I'd rather not be too lean)
It fired right up and we started leaning it up to a smokey 14k
... we stepped back to enjoy the success and it died (wicked hot)

Come to think of it, we did NOTHING to the low end needle at all,
and it idled like a kitten