I'll be the first to admit, I'm not an aircraft engine expert, but don't they have a different fuel/fluid to cold temp start? The fuel evaps/boils more quickly at altitude. That Chebby was running perfectly, I had just got done setting it up with the FAST A/F scanner, best timing was 25° with 93 octane & the fast-burn heads, ran perfectly for about 3 weeks. Then He pulled in complaining it was hard to start, smoking, hard to keep running etc. When I suggested He got a bad load of fuel, He laughed and said "not likely", as He revealed that He had went & filled up with said av-gas. After He ran enough out to add a 1/4 tank pump premium, most of the problems disappeared. Next fillup they were gone.
It's a fact, running more octane than You need results in less mpg & less tq/hp, fact. A gentleman who ran a stock-class 'teener found out after running the stock squeeze combo thru' the ringer, that His best mph/et was on 87. Could He run it on 102 Turbo Blue? Sure, and it would be a pig no matter what timing curve He put in it.
Feel free to educate Me on aircraft operation tho', I'm always glad to learn something.