Heard all the stories, never had a problem....until last weekend. Both my '08 XP AND my buddies '09 XP had sticky throttles all day. Same thing, it always seemed to happen after some "wide-open" riding. You would let off after a pull, and the sled would act like it was still 1/4 throttle. Just like Sherm, we ended up riding "blippin" the throttles. Carb heaters on or off, didn't really seem to make a difference. There was no ice around the throttle block or cable, and temps were around 15-20, with about 2-3" fresh dry powder.
After my ride, I was going over the sled in the shop. I don't remember why, but I pulled the airbox. There was quite a bit ice/water in it. I am wondering, if powder is getting into the airbox, melting, and getting ingested into the carbs, creating a mild momentary carb icing, not allowing the slides to close. Plausible? Today when I was working on my sled, I made sure that the airbox was fully installed and locked into place, and hooked up solidly to the intake. Maybe I was careless and didn't have it fully locked in before, possibly ingesting the powder.
Scary. I didn't like it one bit....