i dunno much about loss of power at higher altitudes but if i were u i'd try getting a better air filter...with free flow induction...like K & N or any of the other better/bigger filters that do away with the air box and have just the cone type filter....for 40-50bux it might be worth a try.....worst case scenario if it doesnt cause improvement...consider it an investment on the car...those things come with a life-time like warranty...so u'll never have to change air filter again