It is actually 3% per 1000 feet. At 10,000 feet, the air is only about 70% as dense and you are only feeding 70% of the fuel so you only get 70% of the HP. So our 104 HP Talon at 10,000 feet is the same as a 72 HP P-1000 at sea level.Isn't it something like 2% power loss per 1000 ft of elevation? I know it seemed like that in my carbureted foreman. The pioneer 1000 honestly didn't feel too much different at 9000ft compared too 300ft in IL. Noticeable, but not 20% less. Oxygen injector lol... turbo should help it seems like.
I can feel a nice difference from 5,000 to 3,000 feet and at 10,000 feet my Talon with 30's is a total dog. IGR will help but the only way to make up for the lack of atmosphere is a turbo!