Just purchased a slightly used (65hrs) unmodified. 08 Teryx. But relocated it from Phoenix AZ.(low country) to High Country AZ. (6500+Elevation). Notice some surging (part throttle cruising) and at this point I will associate this with the Altitude, until I get more familiar with the unit. If any one wishes to chime in with there experience with the Alt change I'd love to open with that. Thanks all and I'm glad I found you.