I have ridden two of the sled's with that Carl's Performance 2009 CFI 660 big bore installed. The big bore is very impressive and the performance feels and "IS" right in line with a very well (Carl's clutch kit) tuned and setup (stock engine and exhaust) 09 800 Dragon in similar track configuration.
The choices are to leave your cylinders stock but improve modifiy your existing sled by porting, head compression, and exhaust. There are concerns that you will find it very challenging to keep alive and get any real additional performance at your lower riding altitudes on 91 fuel.
Once again you can then select a big bore kit. We run several and have for years on the carb style pump 91 from 3500 and up and they are absolutely impressive. Always a performance stand out while being absolutely stock like in reliability. Much below that altitude and then again in different air conditions some have reported requiring higher octane which might make this a no go for your situation.
The 09 is unique in that it is the only 600 that they can and have CFI big bored easily because of this particular years factory setup. I don't know how much variation there is for the CFI mapping on the altitude differences between what has been produced and what you would need. I do know for a fact that one 660 is on it's way to AK so that might tell you something. Carl's would be better to coach you exactly on those recommendations based on their current customer experiences and your expectations.
In conclusion if I owned an 09 Polaris 600CFI sled and was looking for the pop and pull of an 800 with the reliability and "feel" of the 600 that is exactly where my money would go. The kit should run $1600 to $2500 depending on labor and accessories..If a person is serious they can call Chris at Carl's Performance 208-853-5550 for indepth details and accurate pricing
