And presto, the spark turns blue.

Tuning method #2
(suggested by Haynes Manual) is the lift method: using a wire, lift the carb cylinder up a small amount, and it should just slightly increase RPMs if it's in tune. When I tuned it to the colortune, it would actually decrease RPMs under the lift test. I trust the colortune, and I don't have a problem with acceleration, so it seems to work.

Then try to match vacuum

Photo album generated by album tool from Marginal Hacks by David on Wed Jun 3 05:39:55 2015