Brett, we are talking about a race car... the engine will be set on the dyno for maximum output, otherwise its not much of a race engine. Once you get the changes in ambients, the whole schebang goes up the crapper, and your mix gets quite wonky. EFI sees this with its sensors, and accounts for it, so you can still drive hard, even on strange days. This is when the carby cars will be at the back of the pack, and the EFI ones way out in front.