These 2-stroke engines only have 6:1 compression, so technically you only need 87 octane; But I've found that my bikes run a little better (barely noticable) with the good stuff. Maybe it's the other chemicals they put in the good stuff??
In oregon it's 10% in all grades but most stations have the option of Efree but only in 92 octane.Depends on the amount of ethanol. any alcohol will make the engine run leaner. Check your plug or just buy the premium.
It (premium) will not increase power on it's own, however.
or, try them all and see if you can tell which one works best for you. if you can't notice a difference, stick with whatever's cheapest. if you do notice one seems to work better, stick with that, even if it's just your imagination.
it's not like you're going to hurt anything, i mean, not really. it's not a car, it's an oil burning dinosaur designed to run on 1950's gas and motor oil.
and no, premium won't hurt during break in.