"The dealer said they put in premium." I'd take a new sled empty over a free tank from the dealer. I doubt they're having their best guy prepping new sleds, and it's not unlikely somebody either put in cheap gas, or they filled it from something on-hand that'd been sitting around a while. Up to you whether you want to go through the trouble of draining the tank, or add avgas or octane booster to the next fill. Of course, that may not be it, but my guess is this engine is going to be picky about fuel, so eliminating that culprit makes sense. These days, I'd also be giving a new sled a good look-over (like you would with a used sled) before riding it; not saying you're guaranteed to find something, but "they know what they're doing" isn't the best assumption...