There could be several reasons for this situation. One might be a dirty air filter causing air restriction and that would cause the o2 sensors to get coated in raw gas which will cause the EFI/MIL light to come on. There there are people like me that live and ride in higher elevations. For every 1000 feet you go up, you loose about 3% of your power. I ride between 7000 and 12,000 feet so you can imagine. For me without my from and rear windshields on a level road are 6000 feet I can hit 67mph and hit the rev limiter. No so any higher though. But add the resistance of those windshields and my speed drops to about 52 and the RPMs won't go over about 5600 no matter how many colorful words of encouragement it gets...lol. For you I would look at air supply and fuel supply. Make sure she has full pressure and volume on the fuel and that the air filter isn't being restrictive in any way.