What I understand is that there are less oxygen particles per each cubic foot of air at this altitude. N/A engines suck in less oxygen particles because of this. So less oxygen particles means less fuel is needed to maintain the desired AFR. Less fuel burned means less horsepower. Less HP = higher 1/4 mile times. I guess I can say that this is true because the injector pulse width is less here than it is at sea level. I've measured it at both altitudes on the same car.
That's why I want my next car to be turbo, compressing air helps a lot with this condition.
