While riding with the group yesterday the dashboard displayed "malfunction". It felt like there was a loss of power but not to the point where she had any issues running. No misfires, etc. Still easily climbed to 140MPH. I did notice the usual throaty sound from the throttle bodies when I open her up was diminished. When I got her home and was pulling into the garage, the dash said, "STOP - EXHAUST VALVE". I was stopping so I just shut her off. Other than the slight loss of power there were/are no noises coming from the engine. Everything else seems fine. When I start her up she starts fine and there are no warnings on the dash. Only after riding for 15+ minutes does it come back on. I'm completely puzzled. Any thoughts from the guru's?