I'll share my experience but not sure it is the cause of your problem. I did some urban boondocking last week during a snow storm that produced 1.5 foot of snow and 3-4 foot snowdrifts in my subdivision. Sled was an 07 IQ 700RMK and I felt some intermittent bogging that got progressively worse as I continued to track out the fresh powder.
My primary is getting stuck and not releasing/disengaging when I release the throttle and then engine lugs/bogs when I give it more throttle. Haven't pulled the primary yet to take a look but suspect it may be a broken spring. Regardless, it'll be rebuilt when I get some time. Couldn't pull start it either because each pull caused the track to move forward until the primary released....weird..never had that happen before.
Other things:
Fuel: Is fuel fresh? Lots of folks are running 8-9 month old fuel in their sleds first ride of the season.
Fuel filter: When was the last time it was replaced?
Fuel Injector: Perhaps they are clogged, not spraying properly, or stuck partially open. Try a can of BG44k in the tank after replacing fuel filter and see if that helps if fuel filter replacement didn't.
Plugs: I replace mine beginning of every season.
Plug Wires: Check boot connections, check insulation, etc..
Grounding Points: Good clean grounding points for grounding wires are very important for fuel injected sled engines.
Good luck and please share your findings once this is sorted out.