Flex sensor and E-85 :evilb:

I'm going to play around with that in my Holley EFI Mustang build when I eventually install a turbo.

I only run it when I need it like on really hot humid days or when 91oct is all that's available. I definitely don't recommend using it unless absolutely needed.
The car was done for racing half mile competitions but can be driven cross country with active exhaust, NAV, heated/cooled seats, etc without needing a support vehicle. Nothing like driving 1k miles, making 30 passes down a runway at 3x the speed limit, and driving back home. Yearly maintenance is oil change, alignment, sparkplugs, and O2s.

I do not know about Certified Labs Mile-Hi Octane Boost/ Fuel Additive but for Boostane, they have three formulations:
Professional/Racing-Not street legal (I think that means its rough on O2 sensors, etc...)
Premium-Street legal
Marine-Web site says street legal in one place and not street legal in another. "Safe for use with catalytic converters and O2 Sensors."

I'll have to ask him about the o2 sensors and if it causes the orange discoloration on the plugs, Not sure what Boostane cost but this is roughly 38 cents per oz.

I considered (raising a gallon of 87 octane to 92 octane, 5 full octane #s) cost/gallon. I would be interested in your results as I do not want to influence your analysis.

Changed 1 O2 out today. Not orange or red but white/gray. I'll get a pic.

Correct but when I first started using Boostane Professional years ago they said it was O2 safe. It works the best so I'll keep using it as needed. It works better than VP Racing's Octanium.

The MMT orange coating just fouls the plugs/O2s over time and causes a gradual horsepower reduction. Fresh plugs/O2s bring the power right back.

If you have catalytic converters on it, the MMT will plug them up eventually. The car I'm using Boostane Professional in doesn't have cats on it and I get some orange coating inside the exhaust tips if I'm burning a lot of it.