With the airbox removed the sled will run leaner as the restriction of the airbox isn't there... Put the airbox back, its there for a reason. Otherwise you'll need to go up in jet size but you'll need to figure out what jet on your own, theres no published number for the airbox being removed.
I think you ment altitude, latitude shouldn't have much effect on the carb. At higher altitudes the air gets thinner and for reasons I don't really understand you need to go to a larger jet. My 500cc '85 Panther wanted a 300 above 5,000 feet.
Raising sleds from the dead in north central MA.
'70 Ski-Doo Olympique 12/3 - The Yellow Bullet
'71 Arctic Cat Panther 303 - Wankle Panther
'78 Arctic Cat Pantera 5000 - Back from the dead!
'79 Polaris Cobra 340 - Back from the dead!
'95 Ski-Doo Grand Touring SE 670