I have had my 2007 700 XP since new and can get to around 50 MPH with single rider and no windshield. With 2 riders, gear and windshield on I doubt I would get much more that 40 MPH. However, I have never had any issues with sputtering or limiting at max speed and will need to have the experts chime in but never experienced this scenario. It will be interesting to find out what it is!
Craig