Im not a Cobb technician but ive been reading their map notes and it looks like anything below +/- 8 is normal. Depending on the driving conditions like elevation, barometric pressure, and humidity can effect the way the system reads. If you are talking about snowboarding you are probably increasing your elevation which may cause the ECU to compensate for less dense air.
the best advice i can give is to do a few logs and send them in to cobb, they diagnose logs for free and they can give you the best advice to resolve your issue.
hope that helps.
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