I live in Nebraska and travelled to Sturgis, then to Wyoming, thru Estes Park CO. and over the top at 10,000ft. I have a 2006 K9 with V&H pipes, XXX carb, jetted .0295 .078 and a S&S .600 cam. The bike ran fine the entire way, all i had to do is adjust the gas idle mixure screw in during the ride. No rejetting was required. You do loose some power but not much to worry about. If you get on the bike hard you will see a little black smoke come out of the pipe but once again, no big deal.
I was surprised i did not have to rejet, but if the dog spits back thru the carb when riding, turn the gas/air screw in until it quits about 1/2 turn. If you want more information just ask.