Pretty much yeah, above 6000', from what I remember.
Taken from their website: http://www.carlscycle.com/catalog_product_detail.asp?cat=2438-19669&product=1427863
Kit comes with all new ported cast cylinders, billet head set with interchangeable domes, case machining & porting. Complete gasket and seal kits, pistons sets and cylinder studs.
Other items needed but not included with the kit are: SLP single pipe kit, Power Commander 5, SLP motor torque arm and high flow intake, and Carls clutch kit.
Motor will run on premium pump gas at any elevation even at sealevel.
Upper crankcase must be sent in for modification.
"This past season I had the opportunity to ride a Carl's Cycle 900. This potent motor package had tons of bottom end, incredible throttle response and basically more power everywhere. The word that came to mind when I rode it was "FUN!" -CHRIS BURANDT-
Fits: 2011-2013 PRO/RMK 800
For more detailed information, contact our Performance Department at performance@carlscycle.com.