Density altitude will change 1,000 to 1,500 feet throughout a day of racing for me just about everyday.
So you are saying Warren Johnson said proper jetting at a mile high is the same jetting as sea level? Do you think he was compensating in other ways? I don't think you can find any reputable tuning people in the business now that will tell you optimum Jetting wont change at 5,000 feet.