I own a 750 sxi and im wanting to get a impeller for my ski. This ski is my freestyle ski, people say i want a skat trak 9/17 impeller for it. Is this true???? And i have the chance to buy a skat trak 9/17 impeller but it is not a swirl impeller. Its just a regular, How is the performance of the swirl impeller different from a regular one?