down shifting

[qwertydude]

As far as altitude goes, I notice that after about 4000 feet there is a noticeable loss in power, just means shift later on to be in the powerband more. The stock airbox does a decent job in varying altitudes, it was designed to allow for variations in absolute atmospheric pressure due to changes in altitude or temperature. If you switch to a high performance airbox and filter or lunchbox and rejet you'll notice altitude affects your carburation more drastically. I learned this while tuning scooters. Put high performance cone type clamp filters and you get way more power but the jetting was only good for + or - 2000 feet then your jetting was so off you'd lose tons of power, and be performing worse than stock.