Change the fuel filters regardless. If the gas had been in the tank for very long you could precipitate out additives, as well as condensation which can produce schmutz (high-tech motor term.) The choke and higher rpm issues sound just like a fuel supply problem. Get a spare fuel filter at the same time as one load of bad gas can plug one just when you need the motor. Ignore outward appearance of fuel filter; the type of stuff that will plug it won't necessarily be visible. When you remove it, blow through it as well as the new one, and I'll bet you see a significant difference. There is no fuel pump on this motor, to the best of my knowledge, unlike your car, so shmutz has a much quicker effect on fuel delivery. Try this first! If you're going to tear apart your carb I'd recommend that you have someone with you that has done it before; there are lots of little essential parts in there with springs etc and you can have an interesting winter figuring out what you lost or didn't put back correctly.