To add some other stuff.
Seal the intake (remove airbox, make a foam rubber donut to fit between box and throttle bodies and reinstall airbox). Helps to seal the top intakes if you ride chest deep too.
Check your ski rubbers. Fix (weld) where they sit in the spindle too if needed.
Fix the snow flap (replace with something else) if it is still there.
While doing the DD oil check the helix bolts on the secondary. If you still have just 6, IMO it is worth replacing them and loctite (some were not "loctited" from the factory the first year). Change to orange spring while there too and add enough weight to keep it about 7500. Good idea to add a fill hole (casting boss is there) to the DD cover So you don't have to roll the sled for future oil changes. And,,, make sure the speedo wiring is routed and secured properly (if you care about the speedo) while in the area too.
Check the ground bolt (brake side, behind motor, brown wires). They tended to come loose.
Check the brake tail light wiring for a common short you can find with google.
If the sled was trail ridden mostly, the DD brake gets real hot and a fluid change would help alot. Also aggressive riding saw some failures in the front steering shaft (not often in the mountains). Cat had a safety recall and fix that still should be free if it is not done on yours.
Find the vent for the altitude sensor (comes out from the computor, small clear tube) and make sure it is routed and secured somewhere under the y pipe area. Make sure the ethanol plug (same area) is plugged together (they're plenty rich already).
There's a couple of nuts you can snug up (above the pipe) if the handlebars feel a little sloppy.
Look for grease nipples and spritz your thumb lever pivot-TORS area with a bit of silicon spray once in a while.