Honestly if you're planning on going from an 800 Silber axys to a boost, I personally do not think the $12,000 - $15,000 your going to spend to upgrade is worth it. I've had 9 Polaris 800's and 850's all with Silber turbos and have had more headaches with my boost than all the Silber's combined. My boost has spent over 20 days in the dealerships shop for issues not related to the stop rides. My previous 9 Silber turbo sleds never even had 5 days at the dealership combined. I think the Silber 850 kit is the best running most reliable turbo that you can have on a Polaris sled, the only downfall is you have to mix av gas.